Tzai-Hung Wen

• PhD
• Professor at National Taiwan University

The only way for dengue to spread in the human population is through the human-mosquito-human cycle. Most research in this field discusses the dengue-mosquito or dengue-human relationships over a particular study area, but few have explored the local spatial variations of dengue-mosquito and dengue-human relationships within a study area. This stud...

Commuters who acquire dengue infections could be an important route for the transmission of the virus from their homes to workplaces. Understanding the effects of routine human movement on dengue transmission can be helpful in identifying high-risk areas for effective intervention. This study investigated the effects of local environmental and demo...

Epidemic diffusion is a space–time process, and showing time-series disease maps is a common way to demonstrate an epidemic progression in time and space. Previous studies used time-series maps to demonstrate the animation of diffusion process. Epidemic diffusion patterns were determined subjectively by visual inspection, however. There currently a...

Satellite remote sensing is an effective method for extracting water bodies on a large scale. Radar imagery, such as synthetic aperture radar (SAR) imagery, can penetrate clouds and provide opportunities for water body identification when in situ observations are difficult to obtain because of severe weather conditions. However, when using SAR imag...

Dengue fever is a rapidly spreading mosquito-borne disease. Previous studies have shown that dengue vector mosquitoes are weather sensitive, and the effect of temperature on dengue transmission has been confirmed. However, associations between rainfall events and dengue incidence are not consistent, and few studies have addressed the roles of the m...

Air travel is one of the main ways in which contagious diseases spread across regions. State-of-the-art platforms and apps cannot timely and customized estimate exposure risk for air passengers. This study integrated time-varying flight schedules, connecting airports, and epidemic situations in airport catchment areas for estimating a traveler's ex...

Bad road quality brings many problems, such as putting drivers and passengers in danger and causing vehicle suspension system wear. Maintaining high-quality roads relies on regular inspections and repairs, but this is a time-consuming and labor-intensive task. To improve road quality and increase the efficiency of road repairs, an Internet of Thing...

Background The COVID-19 pandemic has profoundly impacted all aspects of human life for over 3 years. Understanding the evolution of public risk perception during these periods is crucial. Few studies explore the mechanisms for reducing disease transmission due to risk perception. Thus, we hypothesize that changes in human mobility play a mediating...

Background The patterns of dengue are affected by many factors, including population density and climate factors. Densely populated areas could play a role in dengue transmission due to increased human-mosquito contacts, the presence of more diverse and suitable vector habitats and breeding sites, and changes in land use. In addition to population...

Background The unprecedented global outbreak of mpox in 2022 posed a public health challenge. In addition to the mpox vaccine campaign in the United States (US), community organisations and public health agencies initiated educational efforts to promote sexual risk reduction. This modelling study estimated the impact of the two-dose vaccination cam...

Identifying clusters or hotspots from disease maps is critical in research and practice. Hotspots have been shown to have a higher potential for transmission risk and may be the source of infections, making them a priority for controlling epidemics. However, the role of edge areas of hotspots in disease transmission remains unclear. This study aims...

Dengue is one of the world’s most rapidly spreading mosquito-borne viral diseases. As it is found mostly in urban and semi-urban areas, urbanization and associated human activities that affect the environment and larval habitats could become risk factors (e.g., lane width, conditions of street ditches) for the spread of dengue. However, there are c...

Before vaccines were introduced, mobility restriction was one of the primary control measures in the early stage of the coronavirus disease 2019 (COVID-19) pandemic. Because different age groups face disproportionate health risks, differences in their mobility changes affect the effectiveness of pandemic control measures. This study aimed to invest...

Dengue fever is a rapidly spreading mosquito-borne contagion. However, the effects of extreme rainfall events on dengue occurrences have not been widely evaluated. With their immense precipitation and high winds, typhoons may have distinct effects on dengue occurrence from those during other heavy rain events. Frequented by typhoons and situated in...

Any distribution of surface features (SFs) exhibits a particular geographic pattern. An understanding of the patterns of geographic data for SFs can help to explain geographic phenomena better, monitor surface conditions, and compare changes in SFs or track their trends. This chapter introduces the methods for analyzing spatial point patterns, incl...

Introduction Containment and closure policies are effective measures used in the early stages of a highly transmissible global pandemic such as COVID-19 to mitigate the spread and reduce transmissions. However, these policies can have negative impacts on the economy and personal freedom. Governments must carefully consider the necessity of increasi...

The rapid spread of a (re)emerging pandemic (e.g., COVID-19) is usually attributed to the invisible transmission caused by asymptomatic cases. Health authorities rely on large-scale voluntary screening to identify and isolate invisible spreaders as well as symptomatic people as early as possible to control disease spread. Raising public awareness i...

Research into geographical invasions of red imported fire ants (RIFAs) by anthropogenic disturbances has received much attention. However, little is known about how land-use change and the characteristics of roads with different land-use types are associated with the risk of RIFA successful invasion or remaining at the highest level of invasion (RI...

Both directly and indirectly transmitted infectious diseases in humans are spatial-related. Spatial dimensions include: distances between susceptible humans and the environments shared by people, contaminated materials, and infectious animal species. Therefore, spatial concepts in managing and understanding emerging infectious diseases are crucial....

Background During the COVID-19 outbreak in Taiwan between May 11 and June 20, 2021, the observed fatality rate (FR) was 5.3%, higher than the global average at 2.1%. The high number of reported deaths suggests that many patients were not treated promptly or effectively. However, many unexplained deaths were subsequently identified as cases, indicat...

The ongoing COVID-19 pandemic has posed a global threat to human health. In order to prevent the spread of this virus, many countries have imposed travel restrictions. This difficult situation has dramatically affected the airline industry by reducing the passenger volume, number of flights, airline flow patterns, and even has changed the entire ai...

Solenopsis invicta Buren, also known as the red imported fire ant (RIFA), has had a large negative impact on human and livestock health. However, few studies have further investigated the influence of human land use, which is an important factor affecting the habitats of insects, on the expansion of RIFAs. In addition, there is a lack of knowledge...

Cyclists can be easily exposed to traffic-related pollutants due to riding on or close to the road during commuting in cities. PM2.5 has been identified as one of the major pollutants emitted by vehicles and associated with cardiopulmonary and respiratory diseases. As routing has been suggested to reduce the exposures for cyclists, in this study, P...

Background During the COVID-19 outbreak in Taiwan between May 11 and June 20, 2021, the observed fatality rate (FR) was 5.3%, higher than the global average at 2.1%. The high number of reported deaths suggests that hospital capacity was insufficient. However, many unexplained deaths were subsequently identified as cases, indicating that there were...

Under the impact of global warming, mosquito‐borne diseases, such as dengue fever, are expanding geographically in subtropical metropolises. Rain‐induced standing water bodies could become mosquito larvae‐favorable environments and trigger disease transmission in high‐populated areas. However, it would be a labor‐intensive campaign to survey possib...

Global pandemic COVID-19 rapidly spreads to many countries, causing enormous economic loss and many deaths in 2020. Low accessibility and availability of medical resources (including screening/testing, prevention, and treatment facilities) for the at-risk populations is an urgent, important issue in preventing and controlling the pandemic. Due to t...

Coronavirus disease 2019 (COVID-19) is an ongoing pandemic that was reported at the end of 2019 in Wuhan, China, and was rapidly disseminated to all provinces in around one month. The study aims to assess the changes in intercity railway passenger transport on the early spatial transmission of COVID-19 in mainland China. Examining the role of railw...

An airline alliance is a group of member airlines that seek to achieve the same goals through routes and airports. Hence, airports’ connectivity plays an essential role in understanding the linkage between different markets, especially the impact of neighboring airports on focal airports. An airline alliance airport network (AAAN) comprises airport...

Restricting human movement to decrease contact probability and frequency helps mitigate large-scale epidemics. Movement-based zoning can be implemented to delineate the boundaries for movement restrictions. Previous studies used network community detection methods, which capture cohesive within-region movements, to delineate containment zones. Howe...

To quickly isolate suspected cases to control the epidemics, this study proposes a body temperature monitoring system with a thermography based on the Internet of things (IoT) architecture. The collected data are transmitted to a back-end platform via wireless communication. Using the analyzed data, the platform provides services such as instant al...

The control strategies preventing subclinical transmission differed among countries. A stochastic transmission model was used to assess the potential effectiveness of control strategies at controlling the COVID-19 outbreak. Three strategies included lack of prevention of subclinical transmission (Strategy A), partial prevention using testing with d...

Dengue fever is a viral disease transmitted by mosquitoes. In recent decades, dengue fever has spread throughout the world. In 2014 and 2015, southern Taiwan experienced its most serious dengue outbreak in recent years. Some statistical models have been established in the past, however, these models may not be suitable for predicting huge outbreaks...

The rapid expansion of coronavirus disease 2019 (COVID-19) has been observed in many parts of the world. Many newly reported cases of COVID-19 during early outbreak phases have been associated with travel history from an epidemic region (identified as imported cases). For those cases without travel history, the risk of wider spreads through communi...

The rapid expansion of coronavirus (COVID-19) has been observed in many parts of the world. Many newly reported cases of this new coronavirus during early outbreak phases have been associated with travel history from an epidemic region (identified as imported cases). For those cases without travel history, the risk of wider spreads through communit...

In recent years, dengue has been rapidly spreading and growing in the tropics and subtropics. Located in southern China, Hong Kong’s subtropical monsoon climate may favour dengue vector populations and increase the chance of disease transmissions during the rainy summer season. An increase in local dengue incidence has been observed in Hong Kong ev...

A novel corona virus (2019-nCoV) was identified in Wuhan, China and has been causing an unprecedented outbreak in China. The spread of this novel virus can eventually become an international emergency. During the early outbreak phase in Wuhan, one of the most important public health tasks is to prevent the spread of the virus to other cities. There...

In recent years, dengue has been rapidly spreading and growing in the tropics and subtropics. Located in southern China, Hong Kong's subtropical monsoon climate may favour dengue vector populations and increase the chance of disease transmissions during the rainy summer season. An increase in local dengue incidence has been observed in Hong Kong ev...

Concentrations of various particulate matter (PM) in urban areas have attracted great attention, due to the increasing demand on life quality. Many studies have highlighted the spatial variability of PM2.5 in urban areas, and found that there are significant differences between residents' exposure and background levels. Different from the strategy...

The basic reproductive number (R 0) is a fundamental measure used to quantify the transmission potential of an epidemic in public health practice. However, R 0 cannot reflect the time-varying nature of an epidemic. A time-varying effective reproductive number R t can provide more information because it tracks the subsequent evolution of transmissio...

A functional region is usually defined as a region characterized by not only interaction cohesiveness but also function diversity. The former indicates that places within a region should share a cohesive interacting pattern of human movements, such as commute or daily travel; the latter means that the places should possess diverse functions like re...

PM2.5 is invisible to the eye, but it is a threat to human health. In order to monitor the small-scale environment status, Taiwan's Environmental Protection Administration (EPA) have deployed more than 2,500 environmental IoT Sensor in 13 cities (Figure 1) to monitor air quality. These sensors are mainly deployed in industrial areas, gather minute-...

Urban air pollution problem has become a huge threat to human health in the most developing and developed countries. Therefore, monitoring air quality with high spatial and temporal resolutions is an important issue. There are two different approaches to mapping street-level distributions of air quality in time and space. One is mathematical approa...

People always need the help of maps when traveling or finding a restaurant. Maps carry geospatial information of a place with roads, landmarks, coordinate systems and so on. When people are reading maps, the first thing our brains do is to fit the map to the realistic environment, trying to integrate the 2-D maps into the 3-D world. In other words,...

Green spaces have benefits but may also increase the risk of allergic disease. This study examined the association between the first occurrence of asthma and greenness exposure in children and teenagers. We conducted a 1:1 matched case-control study matched by sex, age, and the first diagnosis year with 7040 eligible subjects from a systematic samp...

Spatial assimilation is defined as a process whereby, as social status rises, minorities attempt to improve their socioeconomic achievements into an improved spatial position which is primarily dominated by ethnic majorities. Spatial assimilation models examine the immigrants' neighborhood contexts, movements, and their sociodemographic characteris...

Commuting network flows are generally asymmetrical, with commuting behaviors bi-directionally balanced between home and work locations, and with weekday commutes providing many opportunities for the spread of infectious diseases via direct and indirect physical contact. The authors use a Markov chain model and PageRank-like algorithm to construct a...

Tuberculosis (TB) clusters, defined as two or more active TB cases with epidemiological links and the same genotype of Mycobacterium tuberculosis strains, are direct evidence of recent TB transmission. We analyzed TB cases newly diagnosed in 2006-2008, confirmed by the diagnostic laboratory, at a university-affiliated hospital in Taipei metropolita...

Dengue is one of the most rapidly spreading mosquito-borne viral diseases in the world. An increase in the incidence of dengue is commonly thought to be a consequence of variability of weather conditions. Taiwan, which straddles the Tropic of Cancer, is an excellent place to study the relationship between weather conditions and dengue fever cases s...

Purifying selection during dengue viral infection has been suggested as the driving force of viral evolution and the higher complexity of the intra-host quasi-species is thought to offer an adaptive advantage for arboviruses as they cycle between arthropod and vertebrate hosts. However, very few studies have been performed to investigate the viral...

Background: Dengue fever is a vector-borne infectious disease that is transmitted by contact between vector mosquitoes and susceptible hosts. The literature has addressed the issue on quantifying the effect of individual mobility on dengue transmission. However, there are methodological concerns in the spatial regression model configuration for ex...

Human mobility is an important risk factor affecting contagious disease transmission. Therefore, understanding spatial behaviors and interactions among individuals is a fundamental issue. Past studies using high-resolution human contacts data with sequential location data from global positioning systems (GPS) receivers have captured spatial-tempora...

A diffusion process can be considered as the movement of linked events through space and time. Therefore, space-time locations of events are key to identify any diffusion process. However, previous clustering analysis methods have focused only on space-time proximity characteristics, neglecting the temporal lag of the movement of events. We argue t...

The emerging disease of rabies was confirmed in Taiwan ferret badgers (FBs) and reported to the World Organization for Animal Health (OIE) on July 17, 2013. The spread of wildlife rabies can be related to neighborhood countries in Asia. The phylogenetic analysis was conducted by maximum likelihood (ML) methods and the Bayesian coalescent approach b...

Objectives: The risk of tuberculosis (TB) infection within different case-contact contexts is unknown. This study aimed to assess the role of different social contacts in the risk of latent TB infection (LTBI). Methods: We analyzed the records of the TB contact investigation conducted by the Taiwan Centers for Disease Control (CDC) between 2010 and...

For a growing number of developing cities, the capacities of streets cannot meet the rapidly growing demand of cars, causing traffic congestion. Understanding the spatial–temporal process of traffic flow and detecting traffic congestion are important issues associated with developing sustainable urban policies to resolve congestion. Therefore, the...

With the growing number of developing large-scale cities, traffic congestion has becomes a global issue. Traffic congestion could be attributed to topological structure of street network and traffic flow concentration. It is necessary to investigate these two factors simultaneously to solve traffic congestion. Therefore, this study proposed an inno...

The background information of glycoprotein (G) and nucleoprotein (N) reference sequences of the rabies viral strains using in this study for phylogenetic data analysis presented the GenBnak accession number, country source and the year of isolation. The 75 glycoprotein and 63 nucleoprotein of rabies viral strains came from China, Philippines, Thail...

Objectives: Township-level physician-to-population and hospital bed-to-population ratios have been widely adopted as indicators of health care accessibility in Taiwan; however, these indicators cannot reflect actual healthcare-seeking behaviors of patients. Therefore, the aims of this study were to establish actual patient flow for seeking healthca...

Tick-borne ehrlichiosis and mite-borne scrub typhus represent important emerging zoonotic rickettsial diseases. Although scrub typhus has been recognized by the Taiwanese public health system, information on ehrlichial infections is scarce in Taiwan. In this study, the risk of spread of ectoparasites on rodents through aerial and marine transportat...

Effects of climate change on human health become increasingly a growing concern. Especially, the worldwide risk of vector-borne diseases, such as dengue fever, could be strongly influenced by meteorological conditions. Taiwan is unique in terms of its geographical location and abundant ecological environments. It makes Taiwan an unusual epidemic re...

A network approach, which simplifies geographic settings as a form of nodes and links, emphasizes the connectivity and relationships of spatial features. Topological networks of spatial features are used to explore geographical connectivity and structures. The PageR-ank algorithm, a network metric, is often used to help identify important locations...

Understanding the dynamics of how infectious diseases spread in time and space is the primary concern of epidemic control and prevention. Most spatial epidemiological studies use innovative spatial statistical methods to identify spatial or spatial-temporal clusters in an epidemic and their associations with environmental risk factors (Carpenter 20...

Respiratory diseases mainly spread through interpersonal contact. Class suspension is the most direct strategy to prevent the spread of disease through elementary or secondary schools by blocking the contact network. However, as university students usually attend courses in different buildings, the daily contact patterns on a university campus are...

Understanding the spatial characteristics of dengue fever (DF) incidences is crucial for governmental agencies to implement effective disease control strategies. We investigated the associations between environmental and socioeconomic factors and DF geographic distribution, are proposed a probabilistic risk assessment approach that uses threshold-b...

Understanding the spatial characteristics of dengue fever (DF) incidences is crucial for governmental agencies to implement effective disease control strategies. We investigated the associations between environmental and socioeconomic factors and DF geographic distribution, are proposed a probabilistic risk assessment approach that uses threshold-b...

Aedes aegypti (AE) and Aedes albopictus (AA) are the two major dengue vectors in the world. To control dengue, monitoring vectors is essential. The abundance and distribution of mosquitoes are usually considered as a proxy for dengue outbreaks. Most of the researches catch the abundance and distribution of vectors by using traps, but this kind of i...

Immediate treatment with an automated external defibrillator (AED) increases out-of-hospital cardiac arrest (OHCA) patient survival potential. While considerable attention has been given to determining optimal public AED locations, spatial and temporal factors such as time of day and distance from emergency medical services (EMSs) are understudied....

Pluralistic ignorance, a well-documented socio-psychological conformity phenomenon, involves discrepancies between private attitude and public opinion in certain social contexts. However, continuous opinion dynamics models based on a bounded confidence assumption fail to accurately model pluralistic ignorance because they do not address scenarios i...

Air pollution has become a severe environmental problem due to urbanization and heavy traffic. Monitoring street-level air quality is an important issue, but most official monitoring stations are installed to monitor large-scale air quality conditions, and their limited spatial resolution cannot reflect the detailed variations in air quality that m...

Rice straw, a rich agricultural byproduct in Taiwan, can be used as biomass feedstock for cofiring systems. In this study, we analyzed the penetration of rice straw cofiring systems in the Taiwanese power market. In the power generation system, rice straw is cofired with fossil fuel in existing electricity plants. The benefits of cofiring systems i...

Taiwan is located in subtropical and tropical regions with high temperature and high humidity in the summer. This kind of climatic condition is the hotbed for the propagation and spread of the dengue vector mosquito. Kaohsiung City has been the worst dengue fever epidemic city in Taiwan. During the study period, from January 1998 to December 2011,...

Aedes aegypti L. is the primary dengue vector in southern Taiwan. This article is the first report on a large-scale surveillance program to study the spatial-temporal distribution of the local Ae. aegytpi population using ovitraps stratified according to the human population in high dengue-risk areas. The sampling program was conducted for 1 yr and...

From the 2003 severe acute respiratory syndrome (SARS) epidemic, to the 2009 swine-origin influenza A (H1N1) pandemic, to the projected highly pathogenic avian influenza A event, emerging infectious diseases highlight the importance of computational epidemiology to assess potential intervention policies. Hence, an important and timely research goal...

Tuberculosis (TB) disease can be caused by either recent transmission from infectious patients or reactivation of remote latent infection. Spatial dependency (correlation between nearby geographic areas) in tuberculosis incidence is a signature for chains of recent transmission with geographic diffusion. To understand the contribution of recent tra...

Background Taxation of alcohol-containing products may effectively reduce alcohol consumption. However, whether alcohol taxation may lead to a decrease in alcohol-attributed disease mortality (ADM) remains unclear. The objective of this study was to assess the effect of alcohol tax policy in 2002 in Taiwan on temporal changes in geographical dispar...

As irrigation demands usually take the largest share of water supply, paddy fallow is considered as a drought relieving measure in some Asian paddy growing countries by transferring the water saved to the municipal and industrial sectors. But the relationship between fallow area and irrigation demand reduction is not necessarily linear, there may b...

Because air pollutants seriously affect human health, the government in Taiwan attempts to reduce the pollutants by passing many environmental laws and establishing various large-scale and expensive air quality monitoring systems. These monitoring systems are capable of large-scale monitoring, but they cannot immediately detect small-scale air qual...

Air pollution is one of environmental issues that cannot be ignored. The heavy transportation and urbanization result in the air pollutants concentrated in certain areas. Inhaling pollutants for a long time causes damages in human health. Traditional air quality monitoring methods, such as building air quality monitoring stations, are typically exp...

Objectives: An appropriate evaluation of the supply of and demand for physician resources is important for the allocation of medical resource. The current evaluation practice, the townshiplevel physician-to-population ratio, cannot capture the characteristics of cross-district movements of the population. The purpose of this study was to use a geog...