Since the new era of 21st century, despite great progress of medical technology, vaccination programs, and public health systems (Matthew & Mcdonald, 2006), severely infectious diseases, such as the 2003 SARS and the 2009 H1N1, never disappear but evolve into novel ones to cause a series of pandemics, which have demonstrated that infectious events could develop rapidly to interfere with social order and even threaten global stability (Morens, Taubenberger, & Fauci, 2009; Thompson et al., 2003)(Garten, Davis, & Russell, 2009).
At the end of 2019, a novel severe acute respiratory syndrome coronavirus, i.e. COVID-19, rapidly developed and eventually became a global pandemic, causing over 1.6 million cases and 95000 deaths worldwide by April 10, 2020. Wuhan, the capital city of Hubei province in China, was under an early siege to encounter the sudden attack from COVID-19, which almost pushed the medical system to the brink of collapse (Feng, Tang, & Chuai, 2018). The number of cases confirmed in Wuhan has accounted for over 60% of all cases in China by the end of March, 2020. The impact of COVID-19 pandemic is significant and thorough since 1918, resulted in wide-ranging consequences politically and economically.
Compared to the past century, although our modern society has become more robust and resilient to deal with unexpected attacks from hazards, some disruptive factors within urban environments still need to be addressed for the purpose of global health and security. Meanwhile, urban expansion and population agglomeration have increased the risk of encountering epidemic diseases in urban settings, as more than half of the world’s population (55%) have moved to cities by 2018 and this proportion will reach to 68% by 2050 (Lee, Aguilera, & Heymann, 2020). The ongoing pandemic of COVID-19 reminds us of the strong impact of massive urbanization, which has changed the traditional society and needs imperative updates of urban systems to prevent the damage from severe infectious diseases. In order to reduce the threatening of infectious diseases that pose to the metropolitan area with a large population, specific planning strategies adapted to urbanized settings are required based on a better understanding about how infectious diseases transmit in urban environments (Matthew & Mcdonald, 2006).
In the past two months, a plethora of epidemiological investigations on COVID-19 have been made, mainly focusing on the disease characteristics, pathogenic mechanism, and population distribution (Chan, Yuan, & Kok, 2020; Chen, Zhang, & Yang, 2020; Guan, Ni, & Hu, 2020; Lee et al., 2020). However, previous experience with controlling similar diseases, such as SARS, H1N1, and MERS, has proved that effective prevention in advance is more constructive before too many people have been affected by these diseases. Therefore, we face an urgent demand for investigating the spatial pattern of epidemiology and its potential impact on urban lives. Characterizing human-space interactions within urban settings contributes to the prevention of disease transmission (not only COVID-29 but also other infectious diseases), by actively navigating human-mediated process (Stoddard et al., 2013) (Eubank et al., 2004). Analyzing environmental factors of the infectious disease is an indispensable component of understanding the mechanism of transmission (Carlson, Eberle, Kruglyak, & Nickerson, 2004).
As researchers found out, COVID-19 spreads easier and faster than its ancestry SARS, mainly through respiratory droplets of pathogen carriers (Chan et al., 2020). In confined indoor spaces or shared environments with crowded people, the potential aerosol transmission of COVID-19 could be possible, almost catching up to the spread rate of the common influenza. The idea of spatial diffusion, i.e. an outward movement from a single spot to a broader coverage, is conducive to elucidate how this disease spreads in the city through urban flows. Different from the ideal model of even exposure to infectious agents within a homogenous environment, variations in potential disease transmission always happen due to various urban factors (Anderson & May, 1991; Gonzalez, Hidalgo, & Barabasi, 2008), resulting in highly heterogeneous infection patterns within the city (Danon, House, & Keeling, 2009; Lloyd-Smith, Schreiber, Kopp, & Getz, 2005).
Previous studies on SARS have provided evidences to establish associations between the epidemic incidence and urban factors, inferring that the spread of COVID-19 may also follow the similar multidimensional characteristics, which could be reflected in the variation of epidemic situations with demographic conditions, proximity, transportation, and socioeconomic activities (Wang, Meng, Zheng, Liu, & Song, 2005). For instance, the experience of fighting against SARS at Toronto medical systems indicated that the hospital was a major source that introduced higher risks to its surroundings, as the virus could easily transmit not only among health care workers, patients, and hospital visitors, but also make more people and families exposed to infectious environments when pathogen carriers move around the hospital (Affonso, Andrews, & Jeffs, 2004). The clinical uncertainty for such a novel virus makes it more difficult to seize the window period of early control at the beginning of outbreak. Some other spatial-related dimensions in metropolitan areas could also be recognized as essential factors to evaluate the transmission mechanism of COVID-19 in the urban context, as the density of residential blocks, shopping amenities, and the ration relying on mass transportations is extremely high, creating suitable urban environment for the disease transmission (Wang et al., 2005). Moreover, along with the influx of migrants, the squatter settlements with limited housing conditions, sanitation facilities, and access to urban infrastructures, may change the pattern of risks (Lee et al., 2020).
In previous studies, investigations on the epidemiological characteristics and spatiotemporal nature of infectious pandemics on the provincial or national scale seemed prevailing (Mo et al., 2020; Shi, Xiang, Zhang, Chen, & Feng, 2012), whereas few case studies have been carried out to address the impact of urban environment on disease spread specifically based on patients' living locations. Identifying urban environments that may help controlling potential risks becomes increasingly important in the current circumstance. However, it is still difficult to evaluate how the impact varies on the city level as previous epidemiology investigation used to focus on a coarse resolution across provincial or regional boundaries. Therefore, a more incisive investigation with credible location-based details is imperative to further explore the distribution pattern of COVID-19 and influencing urban factors on the city level. We aim to extend the understanding of COVID-19 and its spatial impact not only by validating important urban factors, but also by providing convincing evidence to identify corresponding locations where these factors shed significant influences. Instead of providing a universal antidote, a more precise strategy could be proposed for different areas to better deal with similar public health emergencies in the future, if the spatial variation is taken into consideration.