Yuguo Li

Yuguo Li
The University of Hong Kong | HKU · Department of Mechanical Engineering

PhD

About

413
Publications
149,721
Reads
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22,767
Citations
Additional affiliations
August 2000 - present
The University of Hong Kong
Position
  • Head of Department
August 2000 - May 2016
The University of Hong Kong
Position
  • Professor

Publications

Publications (413)
Article
Full-text available
Pollen is the main factor causing asthma and allergic rhinitis (AR). However, the key indoor and outdoor factors associated with childhood symptoms of allergic rhinitis (SAR) to pollen are unclear. We investigate the association of exposure to outdoor air pollution and indoor environmental factors with childhood SAR to pollen and consider SAR to po...
Article
The phenomenon of vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in high-rise residential buildings (HRRBs) is unique in our densely populated cosmopolitan city. The compulsory testing of a whole building under the scheme of restriction-testing declaration (RTD) during the fourth wave (non-Omicron variant) and...
Article
Leading health authorities have suggested short-range airborne transmission as a major route of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). However, there is no simple method to assess the short-range airborne infection risk or identify its governing parameters. We proposed a short-range airborne infection risk assessment model ba...
Article
The influencing mechanism of droplet transmissions inside crowded and poorly ventilated buses on infection risks of respiratory diseases is still unclear. Based on experiments of one-infecting-seven COVID-19 outbreak with an index patient at bus rear, we conducted CFD simulations to investigate integrated effects of initial droplet diameters(tracer...
Article
Full-text available
Happiness is the foundation of a better life and a goal that people pursue; however, happiness levels among university students are low. The purpose of this study is to explore the main factors influencing student happiness. A nationwide cross-sectional study was conducted in China in 2020. Data on student happiness was collected using the Oxford H...
Article
Poor housing conditions are known to be associated with infectious diseases such as high Coronavirus disease 2019 (COVID-19) incidences. Transmission causes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in poor housing conditions can be complex. An understanding of the exact mechanism of transmission can help to pinpoint contribut...
Article
The COVID-19 pandemic, caused by the virus SARS-CoV-2, has touched most parts of the world and devastated the lives of many. The high transmissibility coupled with the initial poor outcome for the elderly led to crushingly high fatalities. The scientific response to the pandemic has been formidable, aided by advancements in virology, computing, dat...
Article
Responses to the early (February–July 2020) COVID-19 pandemic varied widely, globally. Reasons for this are multiple but likely relate to the healthcare and financial resources then available, and the degree of trust in, and economic support provided by, national governments. Cultural factors also affected how different populations reacted to the v...
Article
A COVID-19 outbreak occurred in May 2020 in a public housing building in Hong Kong – Luk Chuen House, located in Lek Yuen Estate. The horizontal cluster linked to the index case’ flat (flat 812) remains to be explained. Computational fluid dynamics simulations were conducted to obtain the wind-pressure coefficients of each external opening on the e...
Article
In this paper, we develop a mathematical model of the thermal microenvironment in footwear that considers forced ventilation of the footwear cavity. The developed model was validated using a newly developed thermal foot-manikin system and the results show that the model effectively predicts the total dry thermal insulation of footwear under various...
Article
Urban trees affect urban climate via three processes: shading effect, evapotranspiration and wind resistance. However, large differences existed in the performance of different tree species and planting patterns. To quantify the effects of trees, we extended a heat-moisture coupled model by adding a new vegetation sub-model. The results showed that...
Article
Vertical transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) along a vertical column of flats has been documented in several outbreaks of coronavirus disease 2019 (COVID-19) in Guangdong and Hong Kong. We describe an outbreak in Luk Chuen House, involving two vertical columns of flats associated with an unusually connected...
Article
Airborne transmission of SARS-CoV-2 has been increasingly recognized in the outbreak of COVID-19, especially during the emergence of Omicron variant. We investigated an outbreak due to Omicron variant in a restaurant. Besides the epidemiological and phylogenetic analysis, the secondary attack rates of customers of restaurant-related COVID-19 before...
Article
Stack aerosols are generated within vertical building drainage stacks during the discharge of wastewater containing feces and exhaled mucus from toilets and washbasins. Fifteen stack aerosol-related outbreaks of coronavirus disease 2019 (COVID-19) in high-rise buildings have been observed in Hong Kong and Guangzhou. Currently, we investigated two s...
Article
The potential role of aerosol transmission for seasonal respiratory viruses has been dramatically highlighted during the ongoing COVID‐19 pandemic. It is now evident that short‐range (conversational) and long‐range aerosol transmission plays at least some part in how all these respiratory viruses are transmitted between people. This article highlig...
Article
Full-text available
Personal protective behaviors of healthcare workers (HCWs) and dynamic changes in them are known to play a major role in the hospital transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, 1,499 HCWs in Chinese hospitals completed an online survey about their knowledge on SARS-CoV-2 transmission and their perso...
Article
The number of people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to increase worldwide, but despite extensive research, there remains significant uncertainty about the predominant routes of SARS-CoV-2 transmission. We conducted a mechanistic modeling and calculated the exposure dose and infection risk of eac...
Article
The increased intensity of extreme weather events (e.g., heatwaves) that is predicted to occur due to global climate change could significantly impact human health, biodiversity, and infrastructure integrity in cities. As one of the most densely constructed cities in the world, Hong Kong has been experiencing increasingly intense heatwaves in recen...
Article
To explain the observed phenomenon that most SARS‐CoV‐2 transmission occurs indoors whereas its outdoor transmission is rare, a simple macroscopic aerosol balance model is developed to link short‐ and long‐range airborne transmission. The model considers the involvement of exhaled droplets with initial diameter ≤50 µm in the short‐range airborne ro...
Article
Full-text available
The association between the footwear microclimate and microbial community on the foot plantar skin was investigated by experiments with three participants. Novel methods were developed for measuring in-shoe temperature and humidity at five footwear regions, as well as the overall ventilation rate inside the footwear. Three types of footwear were te...
Article
Uncertainty remains on the threshold of ventilation rate in airborne transmission of SARS-CoV-2. We analyzed a COVID-19 outbreak in January 2020 in Hunan Province, China, involving an infected 24-year-old man, Mr. X, taking two subsequent buses, B1 and B2, in the same afternoon. We investigated the possibility of airborne transmission and the venti...
Article
Full-text available
Natural convection arising over vertical and horizontal heated flat surfaces is one of the most ubiquitous flows at a range of spatiotemporal scales. Despite significant developments over more than a century contributing to our fundamental understanding of heat transfer in natural convection boundary layers, certain “hidden” characteristics of thes...
Article
Contaminants, such as pathogens or non-living substances, can spread through the interaction of their carriers (e.g., air and surfaces), which constitute a network. The structure of such networks plays an important role in the contaminant spread. We measured the contaminant spreading efficiency in different networks using a newly defined parameter....
Article
Personal protective behaviors and their dynamic change are known to play a major role in the community spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal pathogen of the coronavirus disease 2019 (COVID-19) pandemic. In this study, a total of 3229 students in Chinese universities completed an online survey about their...
Article
Full-text available
Physical distancing has been an important policy to mitigate the spread of the novel coronavirus disease 2019 (COVID-19) in public settings. However, the current 1–2 m physical distancing rule is based on the physics of droplet transport and could not directly translate into infection risk. We therefore revisit the 2-m physical distancing rule by d...
Article
Debate and scientific inquiries regarding airborne transmission of respiratory infections such as COVID-19 and influenza continue. Health authorities including the WHO and the US CDC have recognized the airborne transmission of COVID-19 in specific settings, although the ventilation requirements remain to be determined. In this work we consider the...
Article
The high-density urban boundary layer (UBL) is one of the most complex atmospheric conditions, while the field data of UBL is limited due to the lack of suitable measurement methods. To better understand the UBL structures in high-density cities, a pioneering investigation is conducted in Hong Kong by Doppler wind LiDAR. Vertical wind speed profile...
Article
Urban heat island (UHI) and cool island (UCI) effects are well-known and prevalent in cities worldwide. An increasing trend of extreme heat events has been observed over the last few decades and is expected to continue in the foreseeable future. In this study, warm periods (May to September) of 2000–2018 were examined to acquire a comprehensive und...
Article
Abstract Public toilets and bathrooms may act as a contact hub point where community transmission of SARS-CoV-2 occurs between users. The mechanism of spread would arise through three mechanisms: inhalation of faecal and/or urinary aerosol from an individual shedding SARS-CoV-2; airborne transmission of respiratory aerosols between users face-to-f...
Article
The incidence of several respiratory viral infections has been shown to be related to climate. Because humans spend most of their time indoors, measures of indoor climate, rather than outdoor climate, may be better predictors of disease incidence and transmission. Therefore, understanding the relationship between indoor and outdoor climate will hel...
Article
Full-text available
By the end of February, 2021, COVID-19 had spread to over 230 countries, with more than 100 million confirmed cases and 2.5 million deaths. To control infection spread with the least disruption to economic and societal activities, it is crucial to implement the various interventions effectively. In this study, we developed an agent-based SEIR model...
Article
Looking further than COVID-19, some of the key messages: 1. We from now on should include the risk of indoor respiratory infections in our design of buildings and its ventilation. 2. Treat the air quality in a similar way as we are used to for water and food quality. 3. ‘Visualize’ the air quality by displaying monitoring values (e.g. CO2 concentra...
Article
Urban surface composition is key information for global carbon emission estimation, mesoscale numerical simulations, and outdoor environment studies at both city and neighborhood scales. High spatial-resolution satellite imagery can provide accurate urban surface data. Due to the large volume of data, it is time-consuming to extract manually inform...
Article
Fomites are known to spread infectious diseases, but their role in determining transmission risk remains unclear. The association of surface touch networks (STNs), proposed to explain this risk, with real-life surface contamination has not yet been demonstrated. To construct STNs, we collected surface touch data from 23–26 scholars through 2 indepe...
Article
Full-text available
Background: Coronavirus disease 2019 (COVID-19) is primarily a respiratory disease that has become a global pandemic. Close contact plays an important role in infection spread, while fomite may also be a possible transmission route. Research during the COVID-19 pandemic has identified long-range airborne transmission as one of the important transmi...
Article
Infectious disease-causing pathogens can be transmitted via contact with contaminated environmental surfaces (i.e., fomite transmission). However, the physical mechanism of fomite transmission remains unclear because of a lack of suitable surrogate tracers. In this study, the non-toxic, non-human-origin and gram-positive bacterium Lactobacillus del...
Article
An outbreak of COVID-19 occurred on the Diamond Princess cruise ship in January and February 2020 in Japan. We analysed information on the cases of infection to infer whether airborne transmission of SARS-CoV-2, the causative agent of COVID-19, had occurred between cabins. We infer from our analysis that most infections in passengers started on 28...
Article
Although airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been recognized, the condition of ventilation for its occurrence is still being debated. We analyzed a coronavirus disease 2019 (COVID-19) outbreak involving three families in a restaurant in Guangzhou, China, assessed the possibility of airborne tran...
Article
The interaction between ambient airflow and human thermal plume may affect airflow distribution in human micro-environment and then personal exposure. This study aims to investigate this interaction and to determine what dominates personal exposure: ambient airflow pattern or local human thermal plume. A computational fluid dynamics (CFD) method wa...
Article
Urban breathability is fundamentally important for improving urban air environment. Nowadays, air pollution and extreme heat waves heavily threaten modern cities and residents. In this paper, a methodology combined with an idealized High-Reynolds-Number Porous-Media city model and a multi-scale Computational Fluid Dynamics (CFD) method will be firs...
Article
Full-text available
COVID-19 threatens the world. Social distancing is a significant factor in determining the spread of this disease, and social distancing is strongly affected by the local travel behaviour of people in large cities. In this study, we analysed the changes in the local travel behaviour of various population groups in Hong Kong, between 1 January and 3...
Article
Full-text available
The Covid-19 pandemic has caused untold disruption and enhanced mortality rates around the world. Understanding the mechanisms for transmission of SARS-CoV-2 is key to preventing further spread but there is confusion over the meaning of “airborne” whenever transmission is discussed. Scientific ambivalence originates from evidence published many yea...
Article
Fomites can transmit some infectious diseases. Human touch behaviors are known to affect virus transmission in buildings. Using video cameras in a graduate student office, we collected more than 98,000 touch actions from 14 h of high-resolution video data of surfaces touched by fingers, palms, and backs of hands. Based on the collected data, we sim...
Article
Full-text available
Surface touch spreads disease-causing microbes, but the measured rates of microbial transfer vary significantly. Additionally, the mechanisms underlying microbial transfer via surface touch are unknown. In this study, a new physical model was proposed to accurately evaluate the microbial transfer rate in a finger-surface touch, based on the mechani...
Article
Background COVID-19 continues to threaten human life worldwide. We explored how human behaviours have been influenced by the COVID-19 pandemic in Hong Kong, and how the transmission of other respiratory diseases (e.g. influenza) has been influenced by human behaviour. Methods We focused on the spread of COVID-19 and influenza infections based on r...
Article
Severe haze episodes and extreme heat events are both related to the strong inversion in the atmospheric boundary layer. Inversion breakup is the main mechanism to alleviate the accumulation of heat or pollutants, especially in urban areas. However, the physical process and turbulent flow structures of inversion breakup remain unclear. In this stud...
Article
Background Non-pharmaceutical interventions (NPIs) against Coronavirus Disease 2019 (COVID-19) are vital to reducing the transmission risks. However, the relative efficiency of social distancing against COVID-19 remains controversial, since social distancing and isolation/quarantine were implemented almost at the same time in China. Methods In thi...
Article
It is essential to understand where and howsevere acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2)is transmitted.Case reports were extracted from the local Municipal Health Commissions of 320prefecturalmunicipalities in China (not including Hubei province). We identified alloutbreaks involving three or more cases and reviewed the major charact...
Article
BACKGROUND: The role of fecal aerosols in the transmission of severe acute respiratory syndrome coronavirus 2 has been suspected. OBJECTIVE: To investigate the temporal and spatial distributions of 3 infected families in a high-rise apartment building and examine the associated environmental variables to verify the role of fecal aerosols. DESIGN: E...
Article
Natural convection flow above a heated horizontal area plays a major role in energy utilisation, indoor/outdoor thermal environment, city ventilation and pollutant dispersion. Such natural convection can present different flow patterns, and identifying the type of flow pattern is crucial for determining the bulk heat transfer coefficient. Water tan...
Article
Full-text available
Introduction Although mounting evidence has linked environmental factors with childhood allergies, some specific key issues still remain unclear: what is the main environmental factor? what is the critical timing window? And whether these contribute to the development of disease? Areas covered This selective review summarizes recent epidemiologica...
Article
Respiratory and fecal aerosols play confirmed and suspected roles, respectively, in transmitting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). An extensive environmental sampling campaign of both toilet and non-toilet environments was performed in a dedicated hospital building for patients with coronavirus disease 2019 (COVID-19), a...
Article
The exact transmission route of many respiratory infectious diseases remains a subject for debate to date. The relative contribution ratio of each transmission route is largely undetermined, which is affected by environmental conditions, human behaviour, the host and the microorganism. In this study, a detailed mathematical model is developed to in...
Article
Full-text available
Understanding the transmission mechanism of SARS-CoV-2 is a prerequisite to effective control measures. To investigate the potential modes of SARS-CoV-2 transmission, 21 COVID-19 patients from 12–47 days after symptom onset were recruited. We monitored the release of SARS-CoV-2 from the patients’ exhaled breath and systematically investigated envir...
Preprint
The coronavirus disease 2019 (COVID-19) is spreading rapidly all over the world. The transmission dynamics of the COVID-19 pandemic is still unclear, but developing strategies for mitigating the severity of the pandemic is yet a top priority for global public health. In this study, we developed a novel compartmental model, SEIR-CV(susceptible-expos...
Article
By 31 March 2020, COVID-19 had spread to more than 200 countries. Over 750,000 confirmed cases were reported, leading to more than 36,000 deaths. In this study, we analysed the efficiency of various intervention strategies to prevent infection by the virus, SARS-CoV-2, using an agent-based SEIIR model, in the fully urbanised city of Shenzhen, Guang...
Article
When background wind is moderate, urban environment may face great challenges as removal ability of airborne pollutants, anthropogenic heat and moisture reduces. Under this condition, buoyancy-driven flow can break the dominant role of the background wind and affect the urban environment greatly. Knowledge of buoyant flow dynamics is essential for...
Article
The adverse environmental impacts of the urban heat island (UHI) phenomenon have been known amid rapid urbanization in many parts of the world. UHI-induced circulation (UHIC) can affect pollutant dispersion and heat exchange. An UHIC can transform into an urban plume (or perturbed UHIC) in the presence of regional wind. To understand the urban plum...
Article
Full-text available
Self-touch may promote the transfer of microorganisms between body parts or surfaces to mucosa. In overt videography of a post-graduate office, students spent 9% of their time touching their own hair, face, neck, and shoulders (HFNS). These data were collected from 274,000 s of surveillance video in a Chinese graduate student office. The non-domina...
Article
Full-text available
Respiratory droplets are bioaerosols that originate from the respiratory tract. Knowing their deposition characteristics during exhalation would facilitate the understanding of the source of large respiratory droplets and their importance in the spread of respiratory infectious diseases. In this study, computational fluid dynamics is used to simula...
Article
Full-text available
The world has been suffering from the COVID-19 pandemic since late 2019. In this study, we compared various types of infection locations in which COVID-19 cases clustered, based on the data from three adjacent provinces in Northeast China. The collected data include all officially reported cases in this area until 8 March 2020. We explored the asso...