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Airborne Transmission of COVID-19: Epidemiologic Evidence from Two Outbreak Investigations

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... Respiratory infections such as COVID-19 are transmitted through droplets (5 to 10 μm) and aerosols (smaller than 5 μm) exhaled from infected individuals when breathing, speaking, coughing, and sneezing (Prather, Wang, and Schooley 2020). Although there is still plenty of uncertainty about the various ways in which COVID-19 contagion occurs (Leung et al. 2020;Han et al. 2020), airborne transmission in closed environments has been established by several authors (Morawska and Cao 2020;Shen et al. 2020;Prather, Wang, and Schooley 2020;Buonanno, Stabile, and Morawska 2020). Consequently, closed environments are generally riskier than open environments (Nishiura et al. 2020;Qian et al. 2020). ...
... Current research suggests that the general advice of keeping a distance of 1.0, 1.5, or 2.0 meters from other people as a precautionary measure works in outdoor environments with short exposure times, but this physical distance rule has been challenged for indoor environments where contagion from an infected to a non-infected person has been reported at larger distances. Shen et al. (2020) report the case of a January 2020 bus trip in Ningbo, China, where a single asymptomatic infected person is believed to have transmitted the COVID-19 virus to 22 passengers (out of 67 persons in total) over two 50-minute bus rides. In this case, the passengers did not wear face masks. ...
... There is, albeit limited, evidence showing that the relevance of physical distancing in public transport can be greatly reduced if other non-pharmaceutical measures are enforced, such as the correct use of face masks, enhanced hygiene, or even a prohibition of talking (Singapore case). On one hand, if contagion in indoor environments can occur at distances greater than two meters due to airborne transmission, as reported by Shen et al. (2020) and further discussed in recent epidemiological contributions (Prather, Wang, and Schooley 2020; Morawska and Cao 2020; Setti et al. 2020), then there is still a risk of virus spreading without wearing a face mask. In the presence of an infected passenger, physical distancing can help reduce the number of people infected but not prevent infection altogether when passengers do not wear masks. ...
Article
Full-text available
The COVID-19 pandemic poses a great challenge for contemporary public transportation worldwide, resulting from an unprecedented decline in demand and revenue. In this paper, we synthesize the state-of-the-art, up to early June 2020, on key developments regarding public transportation and the COVID-19 pandemic, including the different responses adopted by governments and public transportation agencies around the world, and the research needs pertaining to critical issues that minimize contagion risk in public transportation in the so-called post-lockdown phase. While attempts at adherence to physical distancing (which challenges the very concept of mass public transportation) are looming in several countries, the latest research shows that for closed environments such as public transportation vehicles, the proper use of face masks has significantly reduced the probability of contagion. The economic and social effects of the COVID-19 outbreak in public transportation extend beyond service performance and health risks to financial viability, social equity, and sustainable mobility. There is a risk that if the public transportation sector is perceived as poorly transitioning to post-pandemic conditions, that viewing public transportation as unhealthy will gain ground and might be sustained. To this end, this paper identifies the research needs and outlines a research agenda for the public health implications of alternative strategies and scenarios, specifically measures to reduce crowding in public transportation. The paper provides an overview and an outlook for transit policy makers, planners, and researchers to map the state-of-affairs and research needs related to the impacts of the pandemic crisis on public transportation. Some research needs require urgent attention given what is ultimately at stake in several countries: restoring the ability of public transportation systems to fulfill their societal role.
... The Emergence of Physical Distancing Respiratory infections such as COVID-19 are transmitted through droplets (5 to 10 μm) and aerosols (smaller than 5 μm), exhaled from infected individuals when breathing, speaking, coughing, and sneezing (Prather, Wang, and Schooley 2020). Although there is still plenty of uncertainty about the various ways in which COVID-19 contagion occurs (Han et al. 2020;Leung et al. 2020), airborne transmission in closed environments has been recently established by several authors (Buonanno, Stabile, and Morawska 2020;Morawska and Cao 2020;Prather, Wang, and Schooley 2020;Shen et al. 2020). Consequently, closed environments are generally riskier than open environments (Nishiura et al. 2020;Qian et al. 2020). ...
... Current research suggests that the general advice of keeping a distance of 1, 1.5, or 2 meters from other people as a precautionary measure works in outdoor environments with short exposure times, but this physical distance rule has been challenged for indoor environments where contagion from an infected to a non-infected person has been reported at larger distances. Shen et al. (2020) report the case of a January 2020 bus trip in Ningbo, China, where a single asymptomatic infected person is believed to have transmitted the COVID-19 virus to 22 passengers (out of 67 persons in total) over two 50-minute bus rides. In this case, the passengers did not wear face masks. ...
... There is, albeit limited, evidenceshowing that the relevance of physical distancing in public transport can be greatly reduced if other non-pharmaceutical measures are enforced, such as the correct use of face masks, enhanced hygiene, or even a prohibition of talking (Singapore case). On one hand, if contagion in indoor environments can occur at distances greater than two meters due to airborne transmission, as reported byShen et al. (2020) and further discussed in recent epidemiological contributions(Morawska and Cao 2020;Prather, Wang and Schooley 2020;Setti et al. 2020), then there is still a risk of virus spreading without wearing a face mask. In the presence of an infected passenger, physical distancing can help reduce the number of people infected but not prevent infection altogether when passengers do not wear masks. ...
Preprint
Full-text available
The COVID-19 pandemic poses a great challenge for contemporary public transportation worldwide, resulting from an unprecedented decline in demand and revenue. In this paper, we synthesize the state-of-the-art, up to early June 2020, on key developments regarding public transportation and the COVID-19 pandemic, including the different responses adopted by governments and public transportation agencies around the world, and the research needs pertaining to critical issues that minimize contagion risk in public transportation in the so-called post-lockdown phase. While attempts to adherence to physical distancing (which challenges the very concept of mass public transportation) are looming in several countries, the latest research shows that for closed environments such as public transportation vehicles, the proper use of face masks has emerged as significantly reducing the probability of contagion. The economic and social effects of the COVID-19 outbreak in public transportation extend beyond service performance and health risks to financial viability, social equity and sustainable mobility. There is a risk that if the public transportation sector is perceived to poorly transition to the post-pandemic conditions, that perceptions of public transportation as unhealthy will gain ground and might be sustained. To this end, we identify the research needs and outline a research agenda in relation to public health implications of alternative strategies and scenarios, and in particular measures for reducing crowding in public transportation. We provide an overview and an outlook for transport policy makers, planners and researchers to map the state-of-affairs and research needs related to the impacts of the pandemic crisis on public transportation. Some research needs require urgent attention given what is ultimately at stake in several countries: restoring public transportation systems' ability to fulfill its societal role.
... Twenty-eight studies were identified for inclusion in this review. Eight studies represented epidemiological case series of SARS-CoV-2 clusters or outbreaks (with one including a mechanistic analysis), 9,12,13,21,28,[31][32][33] 16 were air sampling studies, 10,11,[14][15][16][17][19][20][21]23,24,29,30,[34][35][36] and four were virological studies. 18,[25][26][27] A summary of the included studies is provided in Table S1. ...
... Eight studies were epidemiological case series assessing outbreaks or clusters of SARS-CoV-2 infection, 9,12,13,21,28,31-33 with one including F I G U R E 1 PRISMA flow diagram a mechanistic element through onsite experiment and computer simulation. 13 Three studies related to cases in China, 9,13,28 two to cases in the United States, 12,32 one to an outbreak in Germany, 33 one to the Diamond Princess cruise ship, 31 and one included a combined analysis of data from China, the United States and Italy. 21 Cai et al. 9 analysed a cluster of infections related to a shopping mall in Wenzhou, China. ...
... Of the four studies employing statistical techniques two were deemed to be appropriate. 13,28 The use of linear regression in the study by Zhang et al. 21 was deemed inappropriate in the context of their analyses, with additional critique in terms of the lack of a control population and the exclusion of a lag time between infection and reported cases. ...
Article
Full-text available
A key consideration in the Covid-19 pandemic is the dominant modes of transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. The objective of this review was to synthesise the evidence for the potential airborne transmission of SARS-CoV-2 via aerosols. Systematic literature searches were conducted in PubMed, Embase, Europe PMC and National Health Service UK evidence up to 27 July 2020. A protocol was published and Cochrane guidance for rapid review methodology was adhered to throughout. Twenty-eight studies were identified. Seven out of eight epidemiological studies suggest aerosol transmission may occur, with enclosed environments and poor ventilation noted as possible contextual factors. Ten of the 16 air sampling studies detected SARS-CoV-2 ribonucleic acid; however, only three of these studies attempted to culture the virus with one being successful in a limited number of samples. Two of four virological studies using artificially generated aerosols indicated that SARS-CoV-2 is viable in aerosols. The results of this review indicate there is inconclusive evidence regarding the viability and infectivity of SARS-CoV-2 in aerosols. Epidemiological studies suggest possible transmission, with contextual factors noted. Viral particles have been detected in air sampling studies with some evidence of clinical infectivity, and virological studies indicate these particles may represent live virus, adding further plausibility. However, there is uncertainty as to the nature and impact of aerosol transmission of SARS-CoV-2, and its relative contribution to the Covid-19 pandemic compared with other modes of transmission.
... There is currently a broad consensus, endorsed by the WHO [1] and the CDC [2], that available data supports the occurrence of direct contagion of the SARS-CoV-2 virus by close range exposure to relatively large droplets emitted by infectious invididuals. While there is also a broad consensus on the factual occurrence of contagion through indirect exposure to smaller submicron droplets (for example [3,4,5,6,7]), its scope and relevance still remains controversial [8,9,10,11,12,13]. ...
... droplets with d p < 5 µm, as opposed to the term "droplets" applied to d p < 5 µm). As we mentioned in the introduction, there is indisputable evidence that indirect exposure to "aerosols" has contributed to SARS-CoV-2 contagion, specially in hospital wards [3,4,5] and clusters in housing and public transport [6,7]. It has been suggested that contagion from "aerosols" play an important role, with authors calling for mitigating measures to better address this issue [8,9,10], arguing to support their case that besides the contagion cases cited before there is experimental evidence that airborne SARS-CoV-2 virus in aerosols has remained viable and stable for periods of typically 3 hours [142,143](and up to 16 hours in [143]). ...
Preprint
We examine the plausibility, scope and risks of aerial transmission of pathogens (including the SARS-CoV-2 virus) through respiratory droplets carried by exhaled e–cigarette aerosol (ECA). Observational and laboratory data suggests considering cigarette smoking and mouth breathing through a mouthpiece as convenient proxies to infer the respiratory mechanics and droplets sizes and their rate of emission that should result from vaping. To infer distances for possible direct contagion we model exhaled ECA flow as an intermittent turbulent jet evolving into an unstable puff, estimating for low intensity vaping (practiced by 80-90% of vapers) ECA expirations the emission of 2-230 respiratory submicron droplets per puff a horizontal distance spread of 1-2 meters, with intense vaping possibly carrying hundreds and up to 1000 droplets per puff in the submicron range a distance spread over 2 meters. Bystanders exposed to low intensity expirations from an infectious vaper in indoor spaces (home and restaurant scenarios) face a 1% increase of risk of indirect contagion with respect to a “control case” scenario defined by exclusively rest breathing without vaping. This relative added risk becomes 5 – 17% for high intensity vaping, 40 – 90% and over 260% for speaking or coughing (without vaping). This risk evaluation remains practically unchanged in shared spaces with universal usage of face masks. We estimate that disinfectant properties of glycols in ECA are unlikely to act efficiently on pathogens carried by vaping expirations under realistic conditions.
... At a call centre in South Korea, more than 43.5% of employees (total number of employees 216) got infected, indicating widespread transmission in a crowded indoor workplace environment (Park et al., 2020). Two people died, and approximately 103 people had tested positive amongst 2460 passengers and about 1111 crew members in Grand Princess cruise ship, USA (Shen et al., 2020). In another case, 24 of 68 people were tested positive on a bus in Ningbo City, Zhejiang Province, China (Shen et al., 2020). ...
... Two people died, and approximately 103 people had tested positive amongst 2460 passengers and about 1111 crew members in Grand Princess cruise ship, USA (Shen et al., 2020). In another case, 24 of 68 people were tested positive on a bus in Ningbo City, Zhejiang Province, China (Shen et al., 2020). Forty people were found with COVID-19 at a shopping mall in Tianjin, China (Tang et al., 2020a). ...
Article
COVID-19 is deemed as the most critical world health calamity of the 21st century, leading to dramatic life loss. There is a pressing need to understand the multi-stage dynamics, including transmission routes of the virus and environmental conditions due to the possibility of multiple waves of COVID-19 in the future. In this paper, a systematic examination of the literature is conducted associating the virus-laden-aerosol and transmission of these microparticles into the multimedia environment, including built environments. Particularly, this paper provides a critical review of state-of-the-art modelling tools apt for COVID-19 spread and transmission pathways. GIS-based, risk-based, and artificial intelligence-based tools are discussed for their application in the surveillance and forecasting of COVID-19. Primary environmental factors that act as simulators for the spread of the virus include meteorological variation, low air quality, pollen abundance, and spatial-temporal variation. However, the influence of these environmental factors on COVID-19 spread is still equivocal because of other non-pharmaceutical factors. The limitations of different modelling methods suggest the need for a multidisciplinary approach, including the ‘One-Health’ concept. Extended One-Health-based decision tools would assist policymakers in making informed decisions such as social gatherings, indoor environment improvement, and COVID-19 risk mitigation by adapting the control measurements.
... Other authors report that the infectivity of viruses in the exhaled air may persist for up to 16 h (Fears et al., 2020). Asynchronous breathing promotes small or tiny drops, usually from the lower respiratory tract, which can linger longer in the environment and travel a longer distance from the infected person (Tang et al., 2020;Shen et al., 2020;Guo et al., 2020). ...
... The experiment demonstrates that the introduction of air conditioning, air purifiers, dust extractors, or other mechanical devices releasing air movement may increase infections among people staying indoors. Our results are consistent with the observations of other authors (Lu et al., 2020;Shen et al., 2020;Moriarty et al., 2020). ...
Article
We aimed to develop a model to quantitatively assess the potential effectiveness of face shield (visor) in reducing airborne transmission risk of the novel coronavirus SARS-CoV-2 during the current COVID-19 pandemic using the computational fluid dynamics (CFD) method. The studies with and without face shield in both an infected and healthy person have been considered in indoor environment simulation. In addition to the influence of the face shield and the synchronization of the breathing process while using the device, we also simulated the effect of small air movements on the SARS-CoV-2 infection rate (outdoor environment simulation). The contact with infectious particles in the case without a face shield was 12–20 s (s), in the presence of at least one person who was positive for SARS-CoV-2. If the infected person wore a face shield, no contact with contaminated air was observed during the entire simulation time (80 s). The time of contact with contaminated air (infection time) decreases to about 11 s when the surrounding air is still and begins to move at a low speed. Qualitative differences between simulations performed on the patients with and without the face shield are clearly visible. The maximum prevention of contagion is probably a consequence of wearing a face shield by an infected person. Our results suggest that it is possible to determine contact with air contaminated by SARS-CoV-2 using the CFD method under realistic conditions for virtually any situation and configuration. The proposed method is probably the fastest and most reliable among those based on CFD-based techniques.
... While 14 geographical settings and data vary, a consistent pattern emerges that public transport has been hit 15 particularly hard compared to private cars and other modes. 16 The decline of public transport ridership is likely due to both authorities' restrictions and travelers' 17 own choices. Public transport stations and vehicles are recognized as high-risk environments for the 18 transmission of COVID-19 due to the limited physical space available, the abundance of surfaces that 19 help spread the virus, and the limited testing of crew and passengers who use the system (Musselwhite 20 et al., 2020;UITP, 2020). ...
... Anecdotal evidence from China further illustrate the propensity for virus transmission on public buses 23 (Shen et al., 2020). 24 ...
Article
Full-text available
The paper analyses the impacts of COVID-19 on daily public transport ridership in the three most populated regions of Sweden (Stockholm, Västra Götaland and Skåne) during spring 2020. The analysis breaks down the overall ridership with respect to ticket types, youths and seniors, and transport modes based on ticket validations, sales and passenger counts data. By utilizing disaggregate ticket validation data with consistent card ids we further investigate to what extent fewer people travelled, or each person travelled less, during the pandemic. The decrease in public transport ridership (40%–60% across regions) was severe compared with other transport modes. Ridership was not restricted by service levels as supply generally remained unchanged throughout the period. The ridership reduction stems primarily from a lower number of active public transport travellers. Travellers switched from monthly period tickets to single tickets and travel funds, while the use and the sales of short period tickets, used predominantly by tourists, dropped to almost zero. One-year period tickets and school tickets increased from mid-April, which could indicate that the travellers using these tickets are particularly captive to the public transport system. Collaborative effort is required to put the results in the international context.
... There is currently a broad consensus, endorsed by the WHO [7] and the CDC [8], that contagion of the SARS-CoV-2 virus occurs either by close range exposure to relatively large droplets emitted by infectious individuals or through indirect exposure to smaller submicron droplets denoted by the term "aerosols" (see, e.g., [9][10][11][12]), although the scope and relevance of each contagion route depend on local factors (volume, occupancy and ventilation regimes of inner spaces) [13][14][15][16][17][18]. The 5 µm cut-off separating larger droplets and "aerosols" is merely a convention that artificially simplifies droplet dynamics that vary along a continuous spectrum of diameters into two mutually exclusive modalities; thus, we avoid as much as possible the binary "droplets" vs. "aerosols" terminology. ...
... Direct exposure to respiratory droplets carried by exhaled ECA can be inferred from the horizontal displacement or penetration distance of the jet/puff system whose dynamics follows from Equations (7)-(10) with the parameter values in (11)- (12). We used the algebraic computing package Maple [112] to plot in Figure 2 the analytic expressions for the displacement distances and centerline velocities for assorted values of initial exhalation velocities U 0 corresponding to the vaping intensities we considered (the Maple worksheets used for the graphs are available through email request to the corresponding author). ...
Article
Full-text available
We examine the plausibility of aerial transmission of pathogens (including the SARS-CoV-2 virus) through respiratory droplets that might be carried by exhaled e-cigarette aerosol (ECA). Given the lack of empiric evidence on this phenomenon, we consider available evidence on cigarette smoking and respiratory droplet emission from mouth breathing through a mouthpiece as convenient proxies to infer the capacity of vaping to transport pathogens in respiratory droplets. Since both exhaled droplets and ECA droplets are within the Stokes regime, the ECA flow acts effectively as a visual tracer of the expiratory flow. To infer quantitatively the direct exposure distance, we consider a model that approximates exhaled ECA flow as an axially symmetric intermittent steady starting jet evolving into an unstable puff, an evolution that we corroborate by comparison with photographs and videos of actual vapers. On the grounds of all this theoretical modeling, we estimate for low-intensity vaping (practiced by 80–90% of vapers) the emission of 6–210 (median 39.9, median deviation 67.3) respiratory submicron droplets per puff and a horizontal distance spread of 1–2 m, with intense vaping possibly emitting up to 1000 droplets per puff in the submicron range with a distance spread over 2 m. The optical visibility of the ECA flow has important safety implications, as bystanders become instinctively aware of the scope and distance of possible direct contagion through the vaping jet.
... Additionally, several outbreak investigation reports revealed that COVID-19 transmission could be especially effective in crowded indoor spaces, such as classrooms, theaters, restaurants or auditoriums [8][9][10]. Mechanical ventilation systems with air recirculation in confined indoor spaces are also associated with increased transmission of respiratory infections and COVID-19 specifically [10][11][12]. ...
Article
Full-text available
The COVID-19 pandemic that has struck the world since March 2019 has established an unusual modus operandi for all of us. During this transient situation, some of the activities have been severely altered, especially those which are performed in indoor spaces such as classrooms, restaurants, or libraries. As physical distance is mandatory in most countries, the capacity of these places has been severely reduced, causing unsustainable economic and logistical issues. This work aims to analyze the possible ways of distributing seats in symmetrical spaces for different uses and room sizes. For that purpose, the classical seat arrangement in rows and columns is compared with an equilateral triangle-based seat pattern, which is proposed as a better solution in most cases. Results show that a greater number of seats is achieved in most situations using the proposed patterns, with mean increases of 13% and peaks from 25% to 50% in some specific circumstances. A discussion about an optimized layout, shape and size of the furniture used in multiple seat tables is included. The outcome shall generate a positive impact on schools, colleges, restaurants, libraries, and similar built environments where seating capacity is crucial.
... According to the information given in [2][3][4][5], if these droplets are large (100 µm), they settle on nearby surfaces within a few seconds. If they are smaller, they float in the air for a few minutes (10 µm) to several days (0.5 µm). ...
Article
Full-text available
In 2020, all the world has been confronted with COVID-19. Bringing people together in buildings is proving to be a risk factor that we have to deal with. Although the greatest attention is paid to the SARS-CoV-2 virus, there are a number of other pathogens (viruses, bacteria, fungi, etc.) that can be transmitted through the air. These pathogens are sensitive to UV-C radiation. UV-C fluorescent lamps have been developed with technical parameters that are adapted to HVAC operating conditions. By using germicidal sources to disinfect the transported air, more than 90% of the SARS-CoV-2 virus, more than 97% of Influenza A virus, and 100% of Legionella pneumophila can be inactivated. The use of UV-C emitters for air disinfection allows the use of circulation and recuperation. Total balance of energy and CO2 emissions by variants and energies used, including humidification were performed for Slovak conditions. The operation of germicidal sources during the heating period in selected cities in our example would represent only 0.45% of the difference in heat demand and 0.42% of the difference in energy demand between operation according to recommendations and operation with germicidal sources. It is therefore an effective means of ensuring health safety and energy efficiency for the future.
... The estimation shows the highest risk of infection among bus and tram drivers in Sweden [19]. Similarly, China demonstrated the evidence of COVID-19 spread on public buses [20]. An analysis of the influences of COVID-19 on daily public transport ridership in the three most populated regions of Sweden during spring 2020 found reduced ridership [21]. ...
Preprint
Full-text available
This study investigates the effect of the coronavirus (COVID-19) pandemic on public transport ridership in Baltimore and nine other U.S. cities similar to Baltimore, in terms of population and service area, during the first five months of 2020. The analysis is based on ridership numbers, vehicle revenue hours, and vehicles operated in maximum service. A compliance analysis was done between 2020 and 2019, as well as a monthly analysis of 2020 by mode and type of services. In comparison to 2019, the ridership decreases from March, the start of the pandemic, while all ten cities experienced the most decrease in ridership in April.
... There are important research evidences that suggest the transmission of Covid-19 through aerosol in indoor spaces. Important publications are related to i.) measurement of Covid-19 in the air, including the distance beyond recommended for the droplet transmission (Van Doremalen et al., 2020;Santarpia et al., 2020;Fears et al., 2020), ii. ) some physically established models of emissions of Covid-19 aerosols and dynamics of those aerosols (Qian et al., 2018;Liu et al., 2017;Riediker & Tsai;, iii.) evidence of airborne transmission for the SARS and MERS infections (Yu et al., 2004;Xiao et al. 2018), iv.) Epidemiological evidences of possible airborne transmission, though other routes cannot be excluded (Shen et al., 2020). The available research evidences support the use of protective measures against transmission of Covid-19 in indoor environments as an addition to other protective strategies already used in practice (for example protective masks, hands hygiene and etc.) (Morawska et al., 2020). ...
Article
Full-text available
Covid-19 causes one of the most alarming global health and economic crises in modern times. Countries around the world establish different preventing measures to stop or control Covid-19 spread. The goal of this paper is to present methods for the evaluation of indoor air quality in public transport to assess the risk of contracting Covid-19. The first part of the paper involves investigating the relationship between Covid-19 and various factors affecting indoor air quality. The focus of this paper relies on exploring existing methods to estimate the number of occupants in public transport. It is known that increased occupancy rate increases the possibility of contamination as well as indoor carbon dioxide concentration. Wireless data collection schemes will be defined that can collect data from public transportation. Collected data are envisioned to be stored in the cloud for data analytics. We will present novel methods to analyze the collected data by considering the historical data and estimate the virus contagion risk level for each public transportation vehicle in service. The methodology is expected to be applicable for other airborne diseases as well. Real-time risk levels of public transportation vehicles will be available through a mobile application so that people can choose their mode of transportation accordingly.
... According to current evidence, COVID-19 virus is primarily transmitted between people through respiratory droplets [9]. Recent publications also provide evidence of airborne transmission [19,4]. Hence, droplet nuclei can also transmit the virus. ...
Preprint
Abstract: Isolation of infected patient seems to be the most effective way to fight against COVID-19. Isolation chamber is a separate room used to isolate patients suffering from highly transmitting infectious diseases. Several rooms for individual patients are allotted and placed together in an isolation unit or isolation chamber. We have proposed a smart isolation chamber comprised of electrode-based air exploser, droplet container and electrode recirculator machine to absorb the viral particles, kill them with a spark and virus get burned instantly. A micro net equipped windows with positive and negative air module will fight against airborne virus. A smart droplet container will prevent transmission of droplets coming from coughing or sneezing. This newly designed isolation chamber will be much more virus transmission preventive compared to the state-of-the-art. This will reduce the new contamination of medical personnel from the patient. The patient also has an opportunity to cure quickly as continuous inhalation of virus particles is minimized. This will reduce the death rate as well as recovering much faster compared to the present scenario.
... For example, it was reported that, in the United States, dozens of members of a choir were infected by SARS-CoV-2 after 2.5 h of rehearsal [30]. In China, clusters of infections were reported in a restaurant and a bus [31,32]. ...
Article
Full-text available
This study calculates and elucidates the minimum size of respiratory particles that are potential carriers of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); furthermore, it evaluates the aerosol generation potential of SARS-CoV-2. The calculations are based on experimental results and theoretical models. In the case of maximum viral-loading derived from experimental data of COVID-19 patients, 7.18 × 10-4% of a respiratory fluid particle from a COVID-19 patient is occupied by SARS-CoV-2. Hence, the minimum size of a respiratory particle that can contain SARS-CoV-2 is calculated to be approximately 4.7 μm. The minimum size of the particles can decrease due to the evaporation of water on the particle surfaces. There are limitations to this analysis: (a) assumption that the viruses are homogeneously distributed in respiratory fluid particles and (b) considering a gene copy as a single virion in unit conversions. However, the study shows that high viral loads can decrease the minimum size of respiratory particles containing SARS-CoV-2, thereby increasing the probability of aerosol generation of the viruses. The aerosol generation theory created in this study for COVID-19 has the potential to be applied to other contagious diseases that are caused by respiratory infectious microorganisms.
... passagers. L'un d'eux était assis à 4,5 mètres de la personne infectée et était entré et sorti de l'autobus par deux portes différentes [27]. ...
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https://www.hcsp.fr/Explore.cgi/AvisRapportsDomaine?clefr=894 SARS-CoV-2 : actualisation des connaissances sur la transmission du virus par aérosols À la suite d’une lettre ouverte adressée à l’Organisation mondiale de la santé (OMS) par 239 scientifiques internationaux le 4 juillet 2020 proposant le reclassement du SARS-CoV-2 comme un virus à transmission aéroportée, l’OMS a demandé de prendre en considération la transmission possible du virus par aérosols et les mesures qui en résultent. Le HCSP lors de précédents avis (8 et 24 avril) n’a pas exclu ce risque de transmission et a déjà émis des recommandations de prévention en milieu intérieur et extérieur. Le présent avis complète ces recommandations pour les milieux intérieurs et les rassemblements extérieurs à forte densité de personnes. Il ne concerne pas le milieu de soins. Il refait le point sur les connaissances disponibles sur l’excrétion respiratoire du virus ainsi que sur les études de modélisations et les expérimentations réalisées sur la transmission aéroportée. L’étude des publications décrivant les contaminations survenues dans des espaces publics clos (restaurant, bus, bateaux de croisières, répétitions de chorales, etc.) et certains milieux professionnels (abattoirs, etc.) fait apparaitre trois conditions favorables à la transmission aéroportée du virus : les conditions de ventilation et de flux d’air, celles de l’atmosphère (basse température, humidité) ainsi que les activités et efforts physiques pratiqués au sein de ces espaces. Le HCSP recommande le port systématique par la population générale d’un masque grand public de préférence en tissu réutilisable (référencé AFNOR S76-001) dans tous les lieux clos publics et privés collectifs ainsi qu’en cas de rassemblement avec une forte densité de personnes en extérieur afin de limiter l’émission de particules respiratoires. Cette mesure est nécessaire pour protéger autrui d’une éventuelle contamination, en particulier les personnes vulnérables. Le HCSP rappelle que doivent être associées à cette recommandation relative au port du masque les autres mesures barrières de distanciation physique, d’hygiène des mains, de nettoyage désinfection des surfaces et d’aération des locaux. Il émet aussi des préconisations en matière de communication sur le port du masque et rappelle les actions de recherche à développer pour mieux connaitre le rôle des aérosols dans la transmission virale. Lire aussi : Réduction du risque de transmission du coronavirus SARS-CoV-2 par la ventilation et gestion des effluents des patients du 17 mars 2020 Coronavirus SARS-CoV-2 : Mesures barrières et de distanciation physique en population générale du 24 avril 2020 Covid-19 : personnes à risque et mesures barrières spécifiques à ces personnes du 20 avril 2020 Coronavirus SARS-CoV-2 : risque de transmission du virus sous formes d’aérosols en milieu intérieur et extérieur du 8 avril 2020 Ministère des solidarités et de la santé : information aux professionnels de santé
... There are important research evidences that suggest the transmission of Covid-19 through aerosol in indoor spaces. Important publications are related to i.) measurement of Covid-19 in the air, including the distance beyond recommended for the droplet transmission (Van Doremalen et al., 2020;Santarpia et al., 2020;Fears et al., 2020), ii. ) some physically established models of emissions of Covid-19 aerosols and dynamics of those aerosols (Qian et al., 2018;Liu et al., 2017;Riediker & Tsai;, iii.) evidence of airborne transmission for the SARS and MERS infections (Yu et al., 2004;Xiao et al. 2018), iv.) Epidemiological evidences of possible airborne transmission, though other routes cannot be excluded (Shen et al., 2020). The available research evidences support the use of protective measures against transmission of Covid-19 in indoor environments as an addition to other protective strategies already used in practice (for example protective masks, hands hygiene and etc.) (Morawska et al., 2020). ...
Article
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Covid-19 causes one of the most alarming global health and economic crises in modern times. Countries around the world establish different preventing measures to stop or control Covid-19 spread. The goal of this paper is to present methods for the evaluation of indoor air quality in public transport to assess the risk of contracting Covid19. The first part of the paper involves investigating the relationship between Covid-19 and various factors affecting indoor air quality. The focus of this paper relies on exploring existing methods to estimate the number of occupants in public transport. It is known that increased occupancy rate increases the possibility of contamination as well as indoor carbon dioxide concentration. Wireless data collection schemes will be defined that can collect data from public transportation. Collected data are envisioned to be stored in the cloud for data analytics. We will present novel methods to analyze the collected data by considering the historical data and estimate the virus contagion risk level for each public transportation vehicle in service. The methodology is expected to be applicable for other airborne diseases as well. Real-time risk levels of public transportation vehicles will be available through a mobile application so that people can choose their mode of transportation accordingly.
... Among them, some could give more evidence of airborne transmission, if they are eventually published. For example, Shen et al. [115] made a comparison between two buses that travelled to the same religious meeting on the same day. An infected person was seated in only one of them, and among the 67 passengers of this bus, 23 cases were revealed (even at a distance greater than 1 m), while no cases occurred in the other bus. ...
Article
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Besides the predominant ways of transmission of SARS-CoV-2 (namely, contacts and large droplets) the airborne one is increasingly taken into consideration as a result of latest research findings. Nevertheless, this possibility has been already suggested by previous studies on other coronaviruses including SARS-CoV and MERS-CoV. To describe the state of the art of coronaviruses and airborne transmission, a systematic review was carried out using the PRISMA methodology. Overall, 64 papers were selected and classified into three main groups: laboratory experiments (12 papers), air monitoring (22) and epidemiological and airflow model studies (30). The airborne transmission of SARS-CoV-2 is suggested by the studies of the three groups, but none has yet obtained complete evidence. The sampling and detection methods have not been validated, therefore monitoring results are a�ected by a possible underestimation. Then, epidemiological investigations only hypothesize the airborne transmission as a possible explanation for some illness cases, but without estimating its attributable risk. Nevertheless, while waiting for more evidence, it is urgent to base advice on preventive measures, such as the use of masks, safe distancing and air ventilation, on the precautionary principle.
... transmission via air (air-borne) is still under contention [29] which has thrown up arguments among researchers. ...
Article
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Coronavirus is no longer a new virus in virology. The novel coronavirus called COVID-19 considering its powerful pathogenicity and transmissibility as confirmed to be more infectious than severe acute respiratory syndrome coronavirus (SARS-COV) and Middle East respiratory syndrome coronavirus (MERS-COV). The method employed in this study is a review of research articles, news and updates on coronavirus (COVID-19) in the area of Nigerian situation, medical laboratory testing and management of the pandemic, based on the political economy of the virus. The recommendations are provided for the Federal School of Medical Laboratory Technology (Science), Jos as an institution and Nigeria through the Federal Ministry of Health. The institution contributes to the control of the pandemic through the provision of hygiene products while expanding her diagnostic services to include COVID-19 diagnosis
... According to current evidence, the COVID-19 virus is primarily infected with respiratory tract infections in humans [14]. Recent publications also provide evidence of airborne transmission [15,16]. Hence, droplet nuclei can also transmit the virus. ...
... https://doi.org/10.1101/2020.06. 10.20127977 doi: medRxiv preprint Also, of note is that there has been a COVID-19 outbreak in Zhejiang Province, China on a bus (16): passengers on the same bus as the index case had an infection risk ratio of 41.5 (95% CI: 2.6-669.5) compared with passengers on another bus. ...
Preprint
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Aims: We aimed to estimate the risk of COVID-19 outbreaks associated with air travel from a country with a very low prevalence of COVID-19 infection (Australia) to a COVID-19-free country (New Zealand; [NZ]), along with the likely impact of various control measures for passengers and cabin crew. Methods: A stochastic version of the SEIR model CovidSIM v1.1, designed specifically for COVID-19 was utilized. It was populated with data for both countries and parameters for SARS-CoV-2 transmission and control measures. We assumed one Australia to NZ flight per day. Results: When no interventions were in place, an outbreak of COVID-19 in NZ was estimated to occur after an average time of 1.7 years (95% uncertainty interval [UI]: 0.04-6.09). However, the combined use of exit and entry screening (symptom questionnaire and thermal camera), masks on aircraft and two PCR tests (on days 3 and 12 in NZ), combined with self-reporting of symptoms and contact tracing and mask use until the second PCR test, reduced this risk to one outbreak every 29.8 years (0.8 to 110). If no PCR testing was performed, but mask use was used by passengers up to day 15 in NZ, the risk was one outbreak every 14.1 years. However, 14 days quarantine (NZ practice in May 2020), was the most effective strategy at one outbreak every 34.1 years (0.06 to 125); albeit combined with exit screening and mask use on flights. Conclusions: Policy-makers can require multi-layered interventions to markedly reduce the risk of importing the pandemic virus into a COVID-19-free nation via air travel. There is potential to replace 14-day quarantine with PCR testing or interventions involving mask use by passengers in NZ. However, all approaches require continuous careful management and evaluation.
... For example, on Feb 3, 2020, in Inner Mongolia of China, a case of COVID-19 was reported in a person who passed the door of a symptomatic patient several times but did not have direct contact, suggesting airborne transmission69 . Another study compared risks of COVID-19 outbreak among 126 passengers taking two buses (59 from Bus #1 and 67 from #2) on a 100-minute round trip in Ningbo, Zhejiang Province70 . Compared to individuals in the non-exposed bus (Bus #1), those in the exposed bus (Bus #2) were 41.5 times more likely to be infected. ...
Article
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As public health teams respond to the pandemic of coronavirus disease 2019 (COVID-19), containment and understanding of the modes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission is of utmost important for policy making. During this time, governmental regulators have been instructing resident with a series of physical distancing measures. However, currently there is no agreement on the role of aerosol transmission for SARS-CoV-2 among public health organizations from different countries. To this end, we aimed to review the evidences of aerosol transmission of SARS-CoV-2. Serval studies support that aerosol transmission of SARS-CoV-2 is plausible, and the plausibility (weight of combined evidence) is 8 out of 9, which is similar to SARS. Precautionary control strategies should consider aerosol transmission for effective mitigation of SARS-CoV-2.
... Besides some major challenges in the international travel, it also impacted sports, entertainment, tourism, hospitality, manufacturing, transportation, and many other sectors. A damage of more than $100 billion is expected to the global aviation industry due to such restrictions [39]. ...
Article
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Coronavirus disease 2019 (COVID-19) is a respiratory illness caused by a virus called SARS-CoV-2. With the global spread of COVID-19, there is a compelling need to improve the health and safety of workers employed in the construction projects (CP). Occupational characteristics, such as interfacing with the public and being in close quarters with other workers, not only put workers at high risk for disease, but also make them a nexus of disease transmission to the community. The objectives of this study are: (1) to evaluate the implications of COVID-19 pandemic on health and safety of workers in construction industry (CI), (2) to analyze the socio-economic-environmental impacts of the pandemic on construction, and (3) to recommend effective ten-point strategy to reduce COVID-19 impacts on the health of construction workers in CP. The required information is collected and analyzed based on the recently published literature, interviews, surveys, and industry experiences. The results reveal that hours of work, wages, workload and stress levels, access to paid leave, interactions with co-workers and supervisors, and health-promoting workplaces have major impacts on the well-being of workers, their families, and their communities. This study will be helpful for the owners, contractors, project managers and owners, and governmental authorities in adopting the effective strategies to improve the health and safety of workers as well as productivity and efficiency in construction projects.
... In an airplane, laboratory-confirmed COVID-19 was detected in 12 patients after a five-hour flight [8]. Based on epidemiological evidence obtained from outbreak investigations, one study reported the possibility of droplet transmission of COVID-19 in a bus [9]. The epidemiological investigations of COVID-19 cases and their close contacts determined that the infection risk is high when passengers are seated within a distance of three rows and five columns from the patient in a train [10]. ...
Article
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Owing to the outbreak of COVID-19, researchers are exploring methods to prevent contact and non-contact infections that occur via multiple transmission routes. However, studies on preventing infections caused by droplet transmission in public transportation are insufficient. To prevent the spread of infectious diseases, a new ventilation system in railway vehicles must be developed. In this study, a novel vertical drop airflow (VDA) system is proposed to mitigate the effect of droplet transmission in a high-speed train cabin. The droplet transmission route and droplet fate are investigated using three-dimensional fluid dynamics simulations, performed employing the Eulerian–Lagrangian model. Additionally, a porous model is adopted to simulate the effect of close-fitting masks. The results indicate that 120 s after coughing, the decrease in the droplet number in the VDA system is 72.1% of that observed in the conventional system. Moreover, the VDA system effectively suppresses droplet transmission because the maximum droplet travel distances of the VDA systems are 49.9% to 67.0% of those of the conventional systems. Furthermore, the effect of reducing droplet transmission by wearing a close-fitting mask is confirmed in all systems. Thus, the decrease in both droplet number and droplet transmission area in train cabins validate that the proposed VDA system has an effective airflow design to prevent droplet infection.
... L'enquête sur deux autres épidémies survenues en Chine en janvier 2020 a considéré les systèmes de climatisation utilisant un mode de recirculation comme une aide probable à la transmission [30,31]. ...
... For example, a reported cluster in Zhejiang province in China, observed that 24 out 67 passengers were infected during a 50-minute bus ride. Interestingly, most of the riders seated adjacent to an open window were not infected [1][2][3]. Another example is the outbreak on the Diamond Princess cruise ship where out of 3711 passengers and crew members on board, more than 700 were infected over a one-month period [4,5]. It was observed that commercial airlines are safer than other transportation modes, due to the utilization of displacement ventilation with air entering from the ceiling and exiting at the floor [6,7] implying that aircraft-like ventilation designs, in which air is not passed among the passengers, are most effective in limiting airborne transmission. ...
Article
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We present in this paper a model of the transport of human respiratory particles on a Charlotte Area Transit System (CATS) bus to examine the efficacy of interventions to limit exposure to SARS-CoV-2, the virus that causes COVID-19. The methods discussed here utilize a commercial Navier–Stokes flow solver, RavenCFD, using a massively parallel supercomputer to model the flow of air through the bus under varying conditions, such as windows being open or the HVAC flow settings. Lagrangian particles are injected into the RavenCFD predicted flow fields to simulate the respiratory droplets from speaking, coughing, or sneezing. These particles are then traced over time and space until they interact with a surface or are removed via the HVAC system. Finally, a volumetric Viral Mean Exposure Time (VMET) is computed to quantify the risk of exposure to the SARS-CoV-2 under various environmental and occupancy scenarios. Comparing the VMET under varying conditions should help identify viable methods to reduce the risk of viral exposure of CATS bus passengers during the COVID-19 pandemic.
... There is, although limited, evidence depicting the significance of physical distancing in public transport can be wholly minimized if other non-pharmaceutical measures are enforced Ngonghala CN, et al. [22], such as the correct use of nose masks and or face masks, enhanced hygiene, or even a prohibition of talking (Singapore case) Cheng VC, et al. [23]; Morawska L, et al. [24], Prather KA, et al. [25]; Shen Y, et al. [26], then there is still a risk of the virus spreading without wearing a nose mask and or face mask. ...
Article
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This study assessed the level of adherence of FUTA shuttle bus operators and passengers to the covid-19 preventive measures suggested by the government, regarding the compulsory hand rinsing; physical distancing preventive measures; and wearing of a nose mask and or face mask in FUTA shuttle bus. Survey research design was employed through personal observation. The observation lasted for 7 days which entails a 7-day peak and off-peak hour count within the specified hours of 7-10 am 2-4 pm and 4-7 pm from Sunday to Saturday. Of the three hours designated for each morning, afternoon, and evening session, there seems to be no rinsing of hands by passengers, although there were provisions of veronica buckets in the Bus Park. Also, there seems to be a low level of adherence to nose masks and or face mask-wearing among the passengers, however, the FUTA shuttle bus operators were keen on ensuring physical distance in the sitting arrangement of passengers as this was discovered in all the shuttle buses that were studied. The study recommends the strict monitoring and enforcement of hand rinsing by passengers in FUTA before the departure of shuttle bus; the enforcement of nose mask and or face mask-wearing inside the shuttle bus.
... 29 Even if simulations in several aircraft have shown a low risk of aerosol dispersal during the flight, 30 multiple outbreaks have occurred during flights, especially long ones and despite low occupancies and prevention measures including wearing masks in some of them. [31][32][33][34][35] Clusters have also been described in other confined spaces like restaurants, 36 conference rooms, or public transportation, 37 and health care facilities have been proven to be among the most contaminated areas by aerosol or contamination transfer. [38][39][40][41][42] Moreover, the virus can survive up to days on surfaces depending on the conditions. ...
Article
In March 2020, COVID-19 caused an overwhelming pandemic. To relieve overloaded Intensive Care Units in the most affected regions, French Ministry of Defence triggered collective Air Medical Evacuations (MEDEVAC) on-board of an Airbus A330 Multi Role Tanker Transport of the French Air Force. Such collective air MEDEVAC is a big challenge regarding biosafety, as until now, only evacuations of a single symptomatic patient with an emergent communicable disease, like Ebola virus disease, have been conducted. However, the COVID-19 pandemic required collective MEDEVAC for critically ill patients and involved a virus still little known. Thus, we performed a complete risk analysis using a process map and an FMECA (Failure Modes, Effects and Criticality Analysis) to assess the risk and implement mitigation measures for health workers, flight crew as well as for the environment. We reported the biosafety management experienced during six flights with a total of 36 critically ill COVID-19 positive patients transferred with no casualties whilst preserving both staffs and aircraft.
... In a restaurant in Guangzhou, nine patrons became infected as a result of their proximity to a recirculating fan coil unit that spread the pathogen up to 5 meters (16 feet) from an infected customer (Lu, et al., 2020). Shen, et al. (2020) document two more events in China, the infection of 23 bus passengers and of 15 conference attendees, in which many of those who contracted COVID-19 were seated more than 2 meters from the carrier. An outbreak in a Korean call centre led to testing of all 1145 building occupants, which found a cluster of 94 cases among individuals who worked on the same floor (Park, et al., 2020). ...
Conference Paper
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Ultraviolet Germicidal Irradiance (UVGI) is the effective technique of inactivating disease-causing bacteria, mould spores, fungi, and viruses using ultraviolet radiation. In this study, we seek to quantify the efficacy and COVID-19 infection risk reduction achieved by UVGI in the upper unoccupied zone of a room so that we may specify the type and placement of UVGI emitters optimally. We present a computational fluid dynamics (CFD) based approach to model disinfection of aerosolized pathogens in a non-uniform ultraviolet field with mixing driven by air exchange and temperature gradients. We validate our CFD against simple calculation methods for UVGI effectiveness in well mixed spaces, and we integrate it with the Wells-Riley model of airborne infection risk to assess the relative benefit of UVGI with and against other measures. We demonstrate an order of magnitude reduction in infection risk as a result of applying UVGI, as well as the ability to quantify infection risk in non-well-mixed settings where simplified calculations methods do not apply.
... Indeed, there is emerging evidence that airborne transmission does occur (Morawska et al., 2020, Shen et al., 2020, which links with thermal comfort and the impact of HVAC systems discussed in section 9.1.1 of this report. Furthermore, we do not yet know the infectious dosethe number of virus particles that someone must be exposed to in order to develop an infection. ...
Article
This report explores multiple strategies and control measures for preventing or limiting the transmission of the SARS-CoV-2 virus in indoor office workplaces. It has been commissioned by Savile Row Projects Ltd to ensure that, in collaboration with its clients and supply chain, its work on the design, installation and operation of office interiors is executed in light of what is known about the disease. The background study on which this report is based focuses on three areas of advice: clinical, behavioural and built environment.
... The risk of catching infection increases with the level of passenger occupancy within the coach and the stations (Tirachini and Cats 2020). The perceived threat results from the airborne nature of Covid-19 virus transmission (Shen et al. 2020). Air conditioning, together with lack of proper ventilation in confined spaces, acts as a facilitator in the spread of infection (Lu et al. 2020;Sun and Zhai 2020). ...
Article
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Availability of safe, reliable and affordable public transport facilitates access to work opportunities. This relationship between transport and economic independence is not gender neutral. Delhi’s Metro Rail Network marked a milestone in this regard as it provided a gender-sensitive means of mass transit with specific facilities for women passengers. However, the onset of Covid-19 pandemic, followed by restrictions on mobility and change in working habits, brought the urban public transport network to a standstill. Given this background, the paper explores the impact of Metro Rail Network on the commuting pattern and preferences of working women in Delhi-NCR region as well as the travel-related challenges faced by women that were magnified during the pandemic.
... However, since the room of the CB buses is very enclosed, passengers will come into contact with each other in the bus, which can also cause the spread of the COVID-19 virus [26]. Shen et al. [27] reported a case of COVID-19 infection among passengers on a bus. It was reported that an asymptomatic infected person transmitted COVID-19 to 22 passengers (out of a total of 67) during two 50-minute bus trips. ...
Article
The COVID-19 epidemic has had a major impact on people’s normal travel. Optimizing the control of the number of passengers boarding and deboarding the customized bus (CB) at CB stops can reduce the contact between passengers in the course of travel, which is meaningful for COVID-19 epidemic prevention and control. In this paper, a dynamic programming model based on nonlinear integer programming (NIP) is established to study the problem of boarding and alighting planning at various CB stops under the influence of COVID-19. Using Gurobi 9.1.1 solver, the optimal plan for passengers boarding and deboarding CB buses could be obtained. Besides, the mathematical model established in this paper can obtain the minimum value of the total number of contacts between passengers during travel under different CB numbers. It is found that the model solution results eventually form a Pareto frontier. When the number of CB buses increases, the total number of contacts between passengers will decrease This study has positive significance for ensuring the normal travel of passengers during the COVID-19 epidemic, and provides useful references for the studies about the planning of the customized bus.
... Research study explaining two additional epidemics from China in January 2020 ascribe air-conditioning systems utilizing a mode of re-transmission as a possible help to virus circulation (Shen et al. 2020). The initial epidemic was linked with a 150-minute incident at a sanctuary. ...
Article
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Substandard ventilation in restricted air-conditioning indoor places is allied with upsurge in the respiratory infections’ transmission. There have been several COVID-19 spread occurrences connected with indoor environment, together with a few from pre-symptomatic situations. Ventilation role in averting coronavirus transmission is not precise (i.e., through inhibiting transmission of an infectious dose to susceptible individuals or preventing the spreading of contagious particles to lessen the risk of transmission). SARS-CoV-2 is believed to be mainly spread through significant respiratory droplets, nevertheless, a growing amount of epidemic information associate aerosol role in the epidemics of coronavirus. Aerosols comprise of droplet nuclei and little droplets which stay in the air for longer than significant droplets. Recent studies show that coronavirus particles can stay transmissible on numerous substances, including aerosols within the indoor environments, as well as the contagion period contingent on humidity and temperature. Thus far, COVID-19 transmission via air-conditioning systems is unclear, but it is considered possible.
Article
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As the world continues to grapple with the reality of coronavirus disease, global research communities are racing to develop practical solutions to adjust to the new challenges. One such challenge is the control of indoor air quality in the COVID-19 era and beyond. Since COVID-19 became a global pandemic, the “super spread” of the virus has continued to amaze policymakers despite measures put in place by public health officials to sensitize the general public on the need for social distancing, personal hygiene, etc. In this work, we have reviewed the literature to demonstrate, by investigating the historical and present circumstances, that indoor spread of infectious diseases may be assisted by the conditions of the HVAC systems. While little consideration has been given to the possibility of indoor airborne transmission of the virus, the available reports have demonstrated that the virus, with average aerodynamic diameter up to 80-120 nm, is viable as aerosol in indoor atmosphere for more than 3 hours, and its spread may be assisted by the HVAC systems. Having reviewed the vulnerability of the conventional ventilation systems, we recommend innovative air circulation concept supported by the use of UVGI in combination with nanoporous air filter to combat the spread of SARS-CoV-2 and other harmful microbes in enclosed spaces.
Article
Covid-19 has become a world pandemic, and Indonesia is among the worse cases. Problems that arise are faced by all parties, including religious elites as well as laypeople. This study was conducted to describe how Muslims in Indonesia responded to and tried to cope with the Covid-19 pandemic. The study uses descriptive qualitative methods to collect data by observation, in-depth interview by phone, and online searching documents. From the research conducted, Islamic mass organizations have a relatively similar opinion that limits religious activities supported by various religious arguments. As for laypeople’s behavior, most are the same as mass organizations and Islamic leaders; very few have different behaviors. In anticipation of the virus spreading, most of them restricted religious activities in full by closing down the mosque and stopping public prayers. Few remained active as before the Covid-19 pandemic. Covid-19 telah menjadi pandemi dunia, dan Indonesia termasuk di antara kasus terparah. Permasalahan yang muncul dihadapi semua pihak, baik elit agama maupun awam. Kajian ini dilakukan untuk mendeskripsikan bagaimana umat Islam di Indonesia menanggapi dan berusaha mengatasi pandemi Covid-19. Penelitian ini menggunakan metode deskriptif kualitatif dengan pengumpulan data melalui observasi, wawancara mendalam melalui telepon, dan pencarian dokumen secara online. Dari penelitian yang dilakukan, ormas Islam memiliki pendapat yang relatif sama yaitu membatasi kegiatan keagamaan yang didukung oleh berbagai dalil keagamaan. Adapun perilaku orang awam, sebagian besar sama dengan ormas dan tokoh Islam; sangat sedikit yang memiliki perilaku berbeda. Untuk mengantisipasi penyebaran virus, sebagian besar dari mereka membatasi kegiatan keagamaan secara penuh dengan menutup masjid dan menghentikan sholat umum. Beberapa tetap aktif seperti sebelum pandemi Covid-19.
Preprint
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Background Evidence for indoor airborne transmission of SARS-CoV-2 is accumulating. If SARS-CoV-2 also spreads via aerosols, this has implications for measures taken to limit transmission. Objectives The aim of this study is to assess exposure to airborne SARS-CoV-2 particles from breathing, speaking, coughing and sneezing in an indoor environment. Methods An exposure assessment model was developed to estimate numbers of SARS-CoV-2 particles in aerosol droplets, expelled during breathing, speaking, coughing and sneezing by an infected person in an unventilated indoor environment, and subsequent inhalation by one or more persons. Scenarios encompass a range of virus concentrations, room sizes and exposure times. Results The calculated total volume of expelled aerosol droplets was highest for a sneeze, followed by a cough and speaking for 20 minutes, and lastly breathing for 20 minutes. A few to as much as tens of millions of virus particles were expelled. Exposure probability strongly depends on the viral concentration in mucus, as well as on the scenario. Exposure probabilities were generally below 1% at a virus concentration in mucus below 10 ⁵ per mL for all scenarios, increasing steeply at different higher concentrations. According to nose / throat swab data collected from patients, 75%, 50% and 5% of infected individuals carry an estimated number of SARS-CoV-2 per mL mucus of at least 10 ⁵ , 10 ⁶ and 10 ⁸ , respectively. Discussion Exposure to SARS-CoV-2 via aerosols generated during breathing, speaking, coughing and sneezing in an unventilated indoor environment is possible. This study forms a basis to estimate probabilities of exposure to SARS-Cov-2 by airborne transmission in indoor spaces. As long as it is uncertain what fraction of the airborne virus particles is infectious and as long as a dose response relation is lacking, it is recommended to be precautious.
Article
Abstrak.Pemerintah telah melakukan berbagai upaya untuk mengurangi resiko penularan Covid-19 misalnya dengan menerapkan sosial distancing maupun Pembatasan Sosial Bersakala Besar (PSBB). Meskipun demikian ada beberapa kegiatan di luar rumah yang masih berjalan, salah satunya adalah kegiatan jual-beli bahan pokok kebutuhan rumah tangga. Para pelaku ekonomi dan pembeli berisiko tertular dan menularkan Covid-19 sehingga perlu adanya kepatuhan protokol kesehatan guna menekan penyebaran Covid-19. Penelitian ini bertujuan untuk mengetahui faktor yang berhubungan dengan penerapan protokol kesehehatan pada pelaku ekonomi khususnya usaha mikro dalam menjalankan usahanya. Metode Penelitian ini yakni observasional analitik dengan rancangan Cross-Sectional . Penelitian ini dilakukan pada bulan Juni sampai Agustus 2020. Populasi pada penelitian ini adalah seluruh pelaku usaha mikro yang berada di Desa Toddotoa Kecamatan Pallangga Kabupaten Gowa. Sampel dalam penelitian ini berjumlah 53 responden yang diambil secara purposive sampling. Hasil penelitian menunjukkan dari 53 responden terdapat 43,4 % menerapkan protokol kesehatan dan 56,6% tidak menerapkan protokol kesehatan. Berdasarkan hasil analisis yang dilakukan maka dapat disimpulkan bahwa pengetahuan (p=0,001), sikap (p=0,000) , PHBS (p=0,000), dan sarana prasarana (p=0,000) berhubungan dengan penerapan protokol kesehatan pada pelaku usaha mikro. Penulran Covid-19 ini sangat cepat sehingga perlu diadakan edukasi kepada warga terkait penyebab penularan Covid-19 diantaranya tidak melakukan Perilaku Hidup Bersih dan Sehat (PHBS) atau Cuci Tangan Pakai Sabun(CTPS) dan faktor lingkungan.
Article
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) causes Coronavirus disease (COVID-19) through multiple transmission routes and understanding the mode of transmission is very important for its containment and prevention. Consequently, inadequate attention has been given to the spread of respiratory droplets in indoor conditions under microclimatologic turbulent wind promoted by aerosol from talking (loud), coughing, sneezing, toilet flushing of an isolation room, and resuspension of the settled virus from the surfaces. To this end, this study is presenting an early review of the process and evidence of aerosol transmission of SARS-CoV-2 particles. There are significant results of many studies including those under peer review that support aerosol and airborne transmission which government agencies should consider for reducing the transmission rate.
Article
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Covid-19 has become a world pandemic, and Indonesia is among the worse cases. Problems that arise are faced by all parties, including religious elites as well as laypeople. This study was conducted to describe how Muslims in Indonesia responded to and tried to cope with the Covid-19 pandemic. The study uses descriptive qualitative methods to collect data by observation, in-depth interview by phone, and online searching documents. From the research conducted, Islamic mass organizations have a relatively similar opinion that limits religious activities supported by various religious arguments. As for laypeople's behavior, most are the same as mass organizations and Islamic leaders; very few have different behaviors. In anticipation of the virus spreading, most of them restricted religious activities in full by closing down the mosque and stopping public prayers. Few remained active as before the Covid-19 pandemic. Abstrak: Covid-19 telah menjadi pandemi dunia, dan Indonesia termasuk di antara kasus terparah. Permasalahan yang muncul dihadapi semua pihak, baik elit agama maupun awam. Kajian ini dilakukan untuk mendeskripsikan bagaimana umat Islam di Indonesia menanggapi dan berusaha mengatasi pandemi Covid-19. Penelitian ini menggunakan metode deskriptif kualitatif dengan pengumpulan data melalui observasi, wawancara mendalam melalui telepon, dan pencarian dokumen secara online. Dari penelitian yang dilakukan, ormas Islam memiliki pendapat yang relatif sama yaitu membatasi kegiatan keagamaan yang didukung oleh berbagai dalil keagamaan. Adapun perilaku orang awam, sebagian besar sama dengan ormas dan tokoh Islam; sangat sedikit yang memiliki perilaku berbeda. Untuk mengantisipasi penyebaran virus, sebagian besar dari mereka membatasi kegiatan keagamaan secara penuh dengan menutup masjid dan menghentikan sholat umum. Beberapa tetap aktif seperti sebelum pandemi Covid-19.
Article
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As countries across the world modify their travel in the face of the Covid-19 pandemic, the first casualty becomes the public transport sector. Transport authorities across the world have reported about 95% reduction in users during peak COVID-19, decrease of fare box revenues and additional costs for disinfecting and implementing physical distancing measures. The public transport companies in India face a larger crisis as nearly 85% people travelling intercity use public road transport in normal times. In this paper we drawpassenger clusters based on their travel dynamics and develop two frameworks, namely, passenger driven transportation strategy framework and epidemic prevention strategy framework to deal with the COVID-19 induced travel changes. The frameworks use three tenets of mobility, namely, agility, integrated movement, and public based partnership. The strategies aim to enable the transport enterprises to open new windows of travel and efficiencies for the passengers rather than restricting access and choices. However, security remains fundamental to making these new and innovative service changes possible. Link to Paper: https://www.sciencedirect.com/science/article/pii/S0967070X21003589?dgcid=author
Article
In April 2020 Transport for London (TfL) commissioned the UCL Department of Civil, Environmental and Geomatic Engineering (CEGE) to explore measures to mitigate the occupational risk posed to London bus drivers from the COVID-19 pandemic, following the tragic deaths of a number of drivers among bus operators within London. A separate study undertaken by UCL’s Institute of Health Equality has examined more comprehensively a number of other risk factors affecting bus drivers, including beyond their occupational risk. Phase one of that study was published on the 27th July 2020 and has determined that “there is evidence that among bus drivers those aged 65 and over, those from BAME backgrounds and those with pre-existing hypertension are at a higher risk of COVID-19 mortality and this should be taken into accounts in efforts by TfL and bus companies to reduce risks”. TfL asked UCL CEGE to explore the nature of this occupational risk in relation to the interaction between passengers and the bus driver, and the effects arising as a result of the design of the bus itself, in particular the assault screen. The assault screen is a pre-existing transparent polycarbonate fixture designed to resist physical attacks, such as stabbings, while allowing the driver to have both a clear view through the screen, access the electronic ticket machine and provide receipts when required, and the ability to be able to hear and speak to passengers as the need arises. It was not originally designed to keep the driver completely isolated from the passengers. A set of detailed models was created of the front part of a typical London bus, including both front and central doors, the driver’s cabin and a detailed dynamic model of the bus driver, and then detailed CFD simulations were carried out. These calculated the motion of aerosols emanating from a passenger who is coughing and breathing in a number of positions relative to the driver’s cabin under a variety of design and operational scenarios in order to identify appropriate interventions. A typical screen and bus design were chosen for the simulations, that addressed all the relevant design issues - gaps, door and window operations - as a representative case for all buses. The original (pre-COVID) designs of polycarbonate dividers or screens were only marginally protective against aerosols and were not sufficient on their own to protect against airborne transmission of SARS-CoV-2. A set of recommendations has been made with the aim of reducing this risk to London drivers in particular as much as is practically possible, further to interventions already initiated by TfL. Buses in large cities are a unique indoor environment that is confined and often crowded at rush hour or in tourist season and, if poorly ventilated there is potential for airborne transmission of infectious diseases which may pose a risk to drivers due to their prolonged exposure times. Further work is required to determine if there may be a risk to passengers too, if they are on board for long journeys. Regardless of any mechanical or physical interventions to reduce risk, it is recommended that in the medium-term, targets for Indoor Air Quality (IAQ) standards on public transport are developed and adopted. This, due to the high number of daily passengers, some of whom have long journey durations (>1hr if commuting from zones 4 and beyond) and the prevalence of infectious diseases such as influenza and the common cold in the population every winter season, which carry large economic costs and also cost lives. The emergence of highly infectious and more dangerous diseases in the UK and around the world in the past two decades, such as SARS-CoV-2, SARS, H1N1 (swine flu) or MERS, all indicate that it is very timely to invest efforts towards maintaining healthy and safe indoor air on public transport.
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The recent COVID-19 pandemic has led to a nearly world-wide shelter-in-place strategy. This raises several natural concerns about the safe relaxing of current restrictions. This article focuses on the design and operation of heating ventilation and air conditioning (HVAC) systems in the context of transportation. Do HVAC systems have a role in limiting viral spread? During shelter-in-place, can the HVAC system in a dwelling or a vehicle help limit spread of the virus? After the shelter-in-place strategy ends, can typical workplace and transportation HVAC systems limit spread of the virus? This article directly addresses these and other questions. In addition, it also summarizes simplifying assumptions needed to make meaningful predictions. This article derives new results using transform methods first given in Ginsberg and Bui. These new results describe viral spread through an HVAC system and estimate the aggregate dose of virus inhaled by an uninfected building or vehicle occupant when an infected occupant is present within the same building or vehicle. Central to these results is the derivation of a quantity called the “protection factor”—a term-of-art borrowed from the design of gas masks. Older results that rely on numerical approximations to these differential equations have long been lab validated. This article gives the exact solutions in fixed infrastructure for the first time. These solutions, therefore, retain the same lab validation of the older methods of approximation. Further, these exact solutions yield valuable insights into HVAC systems used in transportation.
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This review contains an early update on the Covid-19 outbreak. From epidemic status to pandemic status. We reviewed the pattern of spread of Covid-19 across the globe for the first one hundred and twelve days leading to it been described as public health emergency of international concern (PHEIC) and its eventual proclamation as Pandemic. The pneumonia of unknown etiology was initially reported to have occurred in Wuhan city, Hubei province in China. Since its proclamation as a pandemic, the human race, and the global economy had been reconfigured. Every sector of human existence has gotten its share of the outbreak. Within the first fifty days of the outbreak, the major economic powers outside China had confirmed cases of Covid-19 leading to several deaths and shutting down economic activities. During the early days of the virus, Wuhan city, China was the epicenter in the Western Pacific Region (WPR), Italy and Spain the epicenter in the European region with the highest number of deaths recorded in Italy. In the southeast Asian region, India has the highest number of confirmed cases while Iran has the highest in the Eastern Mediterranean corridor, South Africa has the highest confirmed cases in the Africa corridor and the United State of America is the global epicenter with over seven hundred thousand confirmed cases. Globalization fast-tracked the spread of the virus. This review revealed that countries with strong economic powers and natural resources confirmed Covid-19 in the first fifty days and earlier while countries without strong economic identities and natural resources confirmed Covid-19 after eighty days of the outbreak. For the first one hundred and twelve days, over two million confirmed cases and over one hundred and fifty thousand deaths have been recorded globally. The case fatality ratio (CFR) for Covid-19 globally is 6.82% up to 21st April 2020 and this is expected to change in the coming days. In general, over two hundred and ten countries have confirmed cases of Covid-19 for the period under review.
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A new mutated Coronavirus evolved from china during end of year 2019 with the cause of pneumonia and respiratory inflammation. This Coronavirus termed SARS CoV-2 and their associated disease known Covid-19. Covid-19 becomes pandemic through high level of transmission and asymptomatic infection. Their suspective natural host is bat and reached up to human via some intermediate hosts. This spherical Virus has Spike Protein that bind with host ACE-2 receptor and a reason of infection. After entry in host cell, the virus genome (+ssRNA) are replicate with association of double membrane bounded vesicular structure like Endoplasmic reticulum and Golgi bodies and form their associated proteins to develop complete virus. These viruses are expressed through nasopharyngeal or oropharyngeal swab, serological fluids and endotracheal secretion from person to person and animals also. Generally Covid-19 infections are out of control from Immune responses. Some factors like Age of host, Environmental conditions, Geographical and climate are also responsible in infection, transmission and severity. SARS CoV-2 is diagnosed at molecular and serological levels whereas partially influencive treatment is suggesting like antiviral, antifungal and antibiotics drugs. Prevention take as universal truth "Prevention is better than cure", and following through social distancing, use of mask, avoid hand sacking, use of sanitizer etc.
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Introduction A specific model and process of nursing care for patients with COVID-19 has yet to be developed. However, nurses are navigating how to care for patients and themselves in a novel and stressful work environment. A care process is needed that promotes effective nursing for patients’ health and well-being. Objective This study aimed to explore the current nursing care process for patients with COVID-19. Methods The present qualitative study used a grounded theory approach. Participants included 23 nurses working in a hospital COVID-19 ward who were selected through purposive sampling. Semi-structured interviews were conducted with nurses, and data were simultaneously analyzed using MAXQDA software to code the data. Grounded theory with a storyline approach was used to categorize codes to elucidate themes from interviews and check for data saturation. This consists of several steps, including open coding, developing concepts in terms of their properties and dimensions, analyzing data for context, bringing the process into the analysis, and integrating categories. Results Data analysis revealed seven main categories to describe nurses’ conceptions of the care process for COVID-19 patients: ‘patients’ complicated condition’, ‘severe nursing staff shortage’, ‘nursing professionalism’, ‘treatment team collaboration’, ‘work and environmental pressure’, ‘efficacy of care’ and ‘care deficit’. The category of ‘nursing professionalism’ was determined to be the core concept that nurses used to describe their care process. Conclusion Though nurses think highly of their efficacy of care for patients with COVID-19, they face many challenges in their care process that lessen the care they are able to provide for patients and themselves. These include the complex health status of patients, shortage of staff, environmental stresses such as becoming infected, and lack of resources in the hospital. The results of the present study can be used for planning in various fields of nursing, including management, education and clinical training.
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COVID-19 has shown a high potential of transmission via virus-carrying aerosols as supported by growing evidence. However, detailed investigations that draw direct links between aerosol transport and virus infection are still lacking. To fill in the gap, we conducted a systematic computational fluid dynamics (CFD)-based investigation of indoor airflow and the associated aerosol transport in a restaurant setting, where likely cases of airflow-induced infection of COVID-19 caused by asymptomatic individuals were widely reported by the media. We employed an advanced in-house large eddy simulation solver and other cutting-edge numerical methods to resolve complex indoor processes simultaneously , including turbulence, flow-aerosol interplay, thermal effect, and the filtration effect by air conditioners. Using the aerosol exposure index derived from the simulation, we are able to provide a spatial map of the airborne infection risk under different settings. Our results have shown a remarkable direct linkage between regions of high aerosol exposure index and the reported infection patterns in the restaurant, providing strong support to the airborne transmission occurring in this widely reported incident. Using flow structure analysis and reverse-time tracing of aerosol trajectories, we are able to further pinpoint the influence of environmental parameters on the infection risks and highlight the need for more effective preventive measures, e.g., placement of shielding according to the local flow patterns. Our research, thus, has demonstrated the capability and value of high-fidelity CFD tools for airborne infection risk assessment and the development of effective preventive measures.
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The ongoing COVID-19 outbreak has spread rapidly on a global scale. While the transmission of SARS-CoV-2 via human respiratory droplets and direct contact is clear, the potential for aerosol transmission is poorly understood1–3. This study investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the COVID-19 outbreak in February and March 2020. The concentration of SARS-CoV-2 RNA in aerosols detected in isolation wards and ventilated patient rooms was very low, but it was elevated in the patients’ toilet areas. Levels of airborne SARS-CoV-2 RNA in the majority of public areas was undetectable except in two areas prone to crowding, possibly due to infected carriers in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions showing peaks in submicrometre and/or supermicrometre regions, but these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted via aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of aerosolized virus.
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Almost half of the confirmed COVID-19 cases detected so far in the United Kingdom are part of a large cluster of 13 British nationals who tested positive for SARS-CoV-2 in the UK, Spain, and France. Transmissions among this cluster occurred at a ski resort in France, and originated from a single infected traveller returning from a conference in Singapore where he acquired the virus. At least 21 individuals were exposed to the virus, tested, and quarantined, with 13 of those testing positive between the period of 6th February and 15th February. Here, all publicly available information about the primarily UK/France cluster is consolidated, providing a complete and accessible summary of the cases and their connections. Notable in this cluster are the number of individuals infected, the apparent absence of any severe illness among those infected, and a case of a “delayed positive” test during isolation after initially testing negative, at least 7 days after last possible contact.
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Background: The initial cases of novel coronavirus (2019-nCoV)-infected pneumonia (NCIP) occurred in Wuhan, Hubei Province, China, in December 2019 and January 2020. We analyzed data on the first 425 confirmed cases in Wuhan to determine the epidemiologic characteristics of NCIP. Methods: We collected information on demographic characteristics, exposure history, and illness timelines of laboratory-confirmed cases of NCIP that had been reported by January 22, 2020. We described characteristics of the cases and estimated the key epidemiologic time-delay distributions. In the early period of exponential growth, we estimated the epidemic doubling time and the basic reproductive number. Results: Among the first 425 patients with confirmed NCIP, the median age was 59 years and 56% were male. The majority of cases (55%) with onset before January 1, 2020, were linked to the Huanan Seafood Wholesale Market, as compared with 8.6% of the subsequent cases. The mean incubation period was 5.2 days (95% confidence interval [CI], 4.1 to 7.0), with the 95th percentile of the distribution at 12.5 days. In its early stages, the epidemic doubled in size every 7.4 days. With a mean serial interval of 7.5 days (95% CI, 5.3 to 19), the basic reproductive number was estimated to be 2.2 (95% CI, 1.4 to 3.9). Conclusions: On the basis of this information, there is evidence that human-to-human transmission has occurred among close contacts since the middle of December 2019. Considerable efforts to reduce transmission will be required to control outbreaks if similar dynamics apply elsewhere. Measures to prevent or reduce transmission should be implemented in populations at risk. (Funded by the Ministry of Science and Technology of China and others.).
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Background: An ongoing outbreak of pneumonia associated with a novel coronavirus was reported in Wuhan city, Hubei province, China. Affected patients were geographically linked with a local wet market as a potential source. No data on person-to-person or nosocomial transmission have been published to date. Methods: In this study, we report the epidemiological, clinical, laboratory, radiological, and microbiological findings of five patients in a family cluster who presented with unexplained pneumonia after returning to Shenzhen, Guangdong province, China, after a visit to Wuhan, and an additional family member who did not travel to Wuhan. Phylogenetic analysis of genetic sequences from these patients were done. Findings: From Jan 10, 2020, we enrolled a family of six patients who travelled to Wuhan from Shenzhen between Dec 29, 2019 and Jan 4, 2020. Of six family members who travelled to Wuhan, five were identified as infected with the novel coronavirus. Additionally, one family member, who did not travel to Wuhan, became infected with the virus after several days of contact with four of the family members. None of the family members had contacts with Wuhan markets or animals, although two had visited a Wuhan hospital. Five family members (aged 36-66 years) presented with fever, upper or lower respiratory tract symptoms, or diarrhoea, or a combination of these 3-6 days after exposure. They presented to our hospital (The University of Hong Kong-Shenzhen Hospital, Shenzhen) 6-10 days after symptom onset. They and one asymptomatic child (aged 10 years) had radiological ground-glass lung opacities. Older patients (aged >60 years) had more systemic symptoms, extensive radiological ground-glass lung changes, lymphopenia, thrombocytopenia, and increased C-reactive protein and lactate dehydrogenase levels. The nasopharyngeal or throat swabs of these six patients were negative for known respiratory microbes by point-of-care multiplex RT-PCR, but five patients (four adults and the child) were RT-PCR positive for genes encoding the internal RNA-dependent RNA polymerase and surface Spike protein of this novel coronavirus, which were confirmed by Sanger sequencing. Phylogenetic analysis of these five patients' RT-PCR amplicons and two full genomes by next-generation sequencing showed that this is a novel coronavirus, which is closest to the bat severe acute respiatory syndrome (SARS)-related coronaviruses found in Chinese horseshoe bats. Interpretation: Our findings are consistent with person-to-person transmission of this novel coronavirus in hospital and family settings, and the reports of infected travellers in other geographical regions. Funding: The Shaw Foundation Hong Kong, Michael Seak-Kan Tong, Respiratory Viral Research Foundation Limited, Hui Ming, Hui Hoy and Chow Sin Lan Charity Fund Limited, Marina Man-Wai Lee, the Hong Kong Hainan Commercial Association South China Microbiology Research Fund, Sanming Project of Medicine (Shenzhen), and High Level-Hospital Program (Guangdong Health Commission).
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Although short-range large-droplet transmission is possible for most respiratory infectious agents, deciding on whether the same agent is also airborne has a potentially huge impact on the types (and costs) of infection control interventions that are required. The concept and definition of aerosols is also discussed, as is the concept of large droplet transmission, and airborne transmission which is meant by most authors to be synonymous with aerosol transmission, although some use the term to mean either large droplet or aerosol transmission. However, these terms are often used confusingly when discussing specific infection control interventions for individual pathogens that are accepted to be mostly transmitted by the airborne (aerosol) route (e.g. tuberculosis, measles and chickenpox). It is therefore important to clarify such terminology, where a particular intervention, like the type of personal protective equipment (PPE) to be used, is deemed adequate to intervene for this potential mode of transmission, i.e. at an N95 rather than surgical mask level requirement. With this in mind, this review considers the commonly used term of ‘aerosol transmission’ in the context of some infectious agents that are well-recognized to be transmissible via the airborne route. It also discusses other agents, like influenza virus, where the potential for airborne transmission is much more dependent on various host, viral and environmental factors, and where its potential for aerosol transmission may be underestimated.
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Background: With over two billion airline passengers annually, in-flight transmission of infectious diseases is an important global health concern. Many instances of in-flight transmission have been documented, but the relative influence of the many factors (see below) affecting in-flight transmission has not been quantified. Long-standing guidance by public health agencies is that the primary transmission risk associated with air travel for most respiratory infectious diseases is associated with sitting within two rows of an infectious passenger. The effect of proximity may be one of these factors. Objective: The aim of this study was to determine the risk of infection within and beyond the 2-row rule given by public health guidance. Methods: We searched the literature for reports of in-flight transmission of infection which included seat maps indicating where the infectious and infected passengers were seated. Findings: There is a ∼ 6% risk to passengers seated within the 2-rows of infected individual(s) and there is ∼ 2% risk to passengers seated beyond 2-rows from the infectious individual. Discussion: Contact tracing limited to passengers within 2-rows of the infectious individual(s) could fail to detect other cases of infections. This has important consequences for assessing the spread of infectious diseases. Conclusions: Infection at a distance from the index case indicates other factors, such as airflow, movement of passenger/crew members, fomites and contacts between passengers in the departure gate before boarding, or after deplaning, are involved.
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We studied transmission patterns of severe acute respiratory syndrome (SARS) among medical students exposed exclusively to the first SARS patient in the Prince of Wales Hospital in Hong Kong, before his illness was recognized. We conducted a retrospective cohort study of 66 medical students who visited the index patient's ward, including 16 students with SARS and 50 healthy students. The risk of contracting SARS was sevenfold greater among students who definitely visited the index case's cubicle than in those who did not (10/27 [41%] versus 1/20 [5%], relative risk 7.4; 95% confidence interval 1.0 to 53.3). Illness rates increased directly with proximity of exposure to the index case. However, four of eight students who were in the same cubicle, but were not within 1 m of the index case-patient, contracted SARS. Proximity to the index case-patient was associated with transmission, which is consistent with droplet spread. Transmission through fomites or small aerosols cannot be ruled out.
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There is uncertainty about the mode of transmission of the severe acute respiratory syndrome (SARS) virus. We analyzed the temporal and spatial distributions of cases in a large community outbreak of SARS in Hong Kong and examined the correlation of these data with the three-dimensional spread of a virus-laden aerosol plume that was modeled using studies of airflow dynamics. We determined the distribution of the initial 187 cases of SARS in the Amoy Gardens housing complex in 2003 according to the date of onset and location of residence. We then studied the association between the location (building, floor, and direction the apartment unit faced) and the probability of infection using logistic regression. The spread of the airborne, virus-laden aerosols generated by the index patient was modeled with the use of airflow-dynamics studies, including studies performed with the use of computational fluid-dynamics and multizone modeling. The curves of the epidemic suggested a common source of the outbreak. All but 5 patients lived in seven buildings (A to G), and the index patient and more than half the other patients with SARS (99 patients) lived in building E. Residents of the floors at the middle and upper levels in building E were at a significantly higher risk than residents on lower floors; this finding is consistent with a rising plume of contaminated warm air in the air shaft generated from a middle-level apartment unit. The risks for the different units matched the virus concentrations predicted with the use of multizone modeling. The distribution of risk in buildings B, C, and D corresponded well with the three-dimensional spread of virus-laden aerosols predicted with the use of computational fluid-dynamics modeling. Airborne spread of the virus appears to explain this large community outbreak of SARS, and future efforts at prevention and control must take into consideration the potential for airborne spread of this virus.
Article
In December 2019, an outbreak of coronavirus disease 2019 (COVID-19), caused by the virus SARS-CoV-2, began in Wuhan, China (1). The disease spread widely in China, and, as of February 26, 2020, COVID-19 cases had been identified in 36 other countries and territories, including the United States. Person-to-person transmission has been widely documented, and a limited number of countries have reported sustained person-to-person spread.* On January 20, state and local health departments in the United States, in collaboration with teams deployed from CDC, began identifying and monitoring all persons considered to have had close contact† with patients with confirmed COVID-19 (2). The aims of these efforts were to ensure rapid evaluation and care of patients, limit further transmission, and better understand risk factors for transmission.
Preprint
Objective To identify common features of cases with novel coronavirus disease (COVID-19) so as to better understand what factors promote secondary transmission including superspreading events. Methods A total of 110 cases were examined among eleven clusters and sporadic cases, and investigated who acquired infection from whom. The clusters included four in Tokyo and one each in Aichi, Fukuoka, Hokkaido, Ishikawa, Kanagawa and Wakayama prefectures. The number of secondary cases generated by each primary case was calculated using contact tracing data. Results Of the 110 cases examined, 27 (24.6%) were primary cases who generated secondary cases. The odds that a primary case transmitted COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment (95% confidence interval [CI]: 6.0, 57.9). Conclusions It is plausible that closed environments contribute to secondary transmission of COVID-19 and promote superspreading events. Our findings are also consistent with the declining incidence of COVID-19 cases in China, as gathering in closed environments was prohibited in the wake of the rapid spread of the disease.
Preprint
Almost half of the confirmed COVID-19 cases detected so far in the United Kingdom are part of a large cluster of 13 British nationals who tested positive for SARS-CoV-2 in the UK, Spain, and France. Transmissions among this cluster occurred at a ski resort in France, and originated from a single infected traveller returning from a conference in Singapore where he acquired the virus. At least 21 individuals were exposed to the virus, tested, and quarantined, with 13 of those testing positive between the period of 6th Feb and 15th Feb. Here, all publicly available information about the primarily UK/France cluster is consolidated, providing a complete and accessible summary of the cases and their connections. Notable in this cluster are the number of individuals infected, the apparent absence of any severe illness among those infected, and a case of a `delayed positive' test during isolation after initially testing negative, at least 7 days after last possible contact.
Article
An ongoing outbreak of pneumonia associated with 2019 novel coronavirus (2019-nCoV) was reported in China. It is unclear if the infectivity exists during the incubation period, although a person-to-person transmission has been reported in previous studies. We report the epidemiological features of a familial cluster of four patients in Shanghai, of which one was 88 years old man with moving difficulties and was only exposed to his asymptomatic family members who developed symptoms later. The epidemiological evidence has shown a potential transmission of the 2019-nCoV during the incubation period.
Article
Background: In December, 2019, a pneumonia associated with the 2019 novel coronavirus (2019-nCoV) emerged in Wuhan, China. We aimed to further clarify the epidemiological and clinical characteristics of 2019-nCoV pneumonia. Methods: In this retrospective, single-centre study, we included all confirmed cases of 2019-nCoV in Wuhan Jinyintan Hospital from Jan 1 to Jan 20, 2020. Cases were confirmed by real-time RT-PCR and were analysed for epidemiological, demographic, clinical, and radiological features and laboratory data. Outcomes were followed up until Jan 25, 2020. Findings: Of the 99 patients with 2019-nCoV pneumonia, 49 (49%) had a history of exposure to the Huanan seafood market. The average age of the patients was 55·5 years (SD 13·1), including 67 men and 32 women. 2019-nCoV was detected in all patients by real-time RT-PCR. 50 (51%) patients had chronic diseases. Patients had clinical manifestations of fever (82 [83%] patients), cough (81 [82%] patients), shortness of breath (31 [31%] patients), muscle ache (11 [11%] patients), confusion (nine [9%] patients), headache (eight [8%] patients), sore throat (five [5%] patients), rhinorrhoea (four [4%] patients), chest pain (two [2%] patients), diarrhoea (two [2%] patients), and nausea and vomiting (one [1%] patient). According to imaging examination, 74 (75%) patients showed bilateral pneumonia, 14 (14%) patients showed multiple mottling and ground-glass opacity, and one (1%) patient had pneumothorax. 17 (17%) patients developed acute respiratory distress syndrome and, among them, 11 (11%) patients worsened in a short period of time and died of multiple organ failure. Interpretation: The 2019-nCoV infection was of clustering onset, is more likely to affect older males with comorbidities, and can result in severe and even fatal respiratory diseases such as acute respiratory distress syndrome. In general, characteristics of patients who died were in line with the MuLBSTA score, an early warning model for predicting mortality in viral pneumonia. Further investigation is needed to explore the applicability of the MuLBSTA score in predicting the risk of mortality in 2019-nCoV infection. Funding: National Key R&D Program of China.
Article
The concept of aerosol transmission is developed to resolve limitations in conventional definitions of airborne and droplet transmission. The method was literature review. An infectious aerosol is a collection of pathogen-laden particles in air. Aerosol particles may deposit onto or be inhaled by a susceptible person. Aerosol transmission is biologically plausible when infectious aerosols are generated by or from an infectious person, the pathogen remains viable in the environment for some period of time, and the target tissues in which the pathogen initiates infection are accessible to the aerosol. Biological plausibility of aerosol transmission is evaluated for Severe Acute Respiratory Syndrome coronavirus and norovirus and discussed for Mycobacterium tuberculosis, influenza, and Ebola virus. Aerosol transmission reflects a modern understanding of aerosol science and allows physically appropriate explanation and intervention selection for infectious diseases.
Article
Measles cases are increasing in Ireland, with 320 cases notified since August 2009. Nearly two-thirds of these cases (n=206) were unvaccinated. In the early stages of the outbreak a substantial number of cases were linked to the Traveller community with some cases also reported among the Roma community, other citizens from eastern Europe and children whose parents objected to vaccination. By February 2010, there had been considerable spread to the general population.
Article
A jet airliner with 54 persons aboard was delayed on the ground for three hours because of engine failure during a takeoff attempt. Most passengers stayed on the airplane during the delay. Within 72 hours, 72 per cent of the passengers became ill with symptoms of cough, fever, fatigue, headache, sore throat and myalgia. One passenger, the apparent index case, was ill on the airplane, and the clinical attack rate among the others varied with the amount of time spent aboard. Virus antigenically similar to A/Texas/1/77(H3N2) was isolated from 8 of 31 passengers cultured, and 20 of 22 ill persons tested had serologic evidence of infection with this virus. The airplane ventilation system was inoperative during the delay and this may account for the high attack rate.
Article
Two solutions are proposed for the estimation of odds ratios (OR) when one or the two elements of the principal (A, D) or secondary (B, C) diagonals of a 2 x 2 matrix (A, B, C, D) are 0. The OR estimate is AD/BC. If A or D are 0, OR = 0; if B or C are 0, the OR is undefined. Analytical solution. This solution conserves the marginal totals. If B = 0 and C = 0, the OR cannot be less than AD/1 (the minimal acceptable value), then the equation (A-X) (D-X)/X2 = KAD/1 searches for that X which subtracted to A and B and added to B (0) and C (0) yields an OR K times AD; if B = 0 and C > 0 then (A-X) (D-X)/X (C+X) = AD/C; if B > 0 and C = 0, then B replaces C in the latter equation. If A and D are 0, X2/(B-X) (C-X) = 1/KBC; if A = 0 and D > 0, X (D+X)/(B-X) (C-X) = D/KBC; if A > 0 and D = 0, A replaces D in the latter equation. K can be taken at the maximum Chi squared value. Probabilistic solution. Zeros are replaced by ones and the elements of the diagonal without zeros are increased proportionally until the exact probability (Fisher) of this new matrix is equal or the nearest less than the exact probability of the original matrix. Since small numbers increase the estimation bias, the Haldane's correction should be always applied. This correction adds 0.5 to A, B C and D to estimate the OR (In OR) and adds 1 to these elements to estimate their variance.
Article
The severe acute respiratory syndrome (SARS) spread rapidly around the world, largely because persons infected with the SARS-associated coronavirus (SARS-CoV) traveled on aircraft to distant cities. Although many infected persons traveled on commercial aircraft, the risk, if any, of in-flight transmission is unknown. We attempted to interview passengers and crew members at least 10 days after they had taken one of three flights that transported a patient or patients with SARS. All index patients met the criteria of the World Health Organization for a probable case of SARS, and index or secondary cases were confirmed to be positive for SARS-CoV on reverse-transcriptase polymerase chain reaction or serologic testing. After one flight carrying a symptomatic person and 119 other persons, laboratory-confirmed SARS developed in 16 persons, 2 others were given diagnoses of probable SARS, and 4 were reported to have SARS but could not be interviewed. Among the 22 persons with illness, the mean time from the flight to the onset of symptoms was four days (range, two to eight), and there were no recognized exposures to patients with SARS before or after the flight. Illness in passengers was related to the physical proximity to the index patient, with illness reported in 8 of the 23 persons who were seated in the three rows in front of the index patient, as compared with 10 of the 88 persons who were seated elsewhere (relative risk, 3.1; 95 percent confidence interval, 1.4 to 6.9). In contrast, another flight carrying four symptomatic persons resulted in transmission to at most one other person, and no illness was documented in passengers on the flight that carried a person who had presymptomatic SARS. Transmission of SARS may occur on an aircraft when infected persons fly during the symptomatic phase of illness. Measures to reduce the risk of transmission are warranted.
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WHO recommended measures for persons undertaking international travel from areas affected by severe acute respiratory syndrome (SARS)
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