Field study to characterize customer flow and ventilation rates in retail buildings in Shenzhen, China

Correlations between the urban built environmental factors and the spatial distribution at the community level in the reported COVID-19 samples: A case study of Wuhan

COVID-19 has dramatically changed the lifestyle of people, especially in urban environments. This paper investigated the variations of built environments that were measurably associated with the spread of COVID-19 in 150 Wuhan communities. The incidence rate in each community before and after the lockdown (January 23, 2020), as respective dependent variables, represented the situation under normal circumstances and non-pharmaceutical interventions (NPI). After controlling the population density, floor area ratio (FAR), property age and sociodemographic factors, the built environmental factors in two spatial dimensions, the 15-minute walking life circle and the 10-minute cycling life circle, were brought into the Hierarchical Linear Regression Model and the Ridge Regression Model. The results indicated that before lockdown, the number of markets and schools were positively associated with the incidence rate, while community population density and FAR were negatively associated with COVID-19 transmission. After lockdown, FAR, GDP, the number of hospitals (in the 15-minute walking life circle) and the bus stations (in the 10-minute cycling life circle) became negatively correlated with the incidence rate, while markets remained positive. This study effectively extends the discussions on the association between the urban built environment and the spread of COVID-19. Meanwhile, given the limitations of sociodemographic data sources, the conclusions of this study should be interpreted and applied with caution.

Comparison of COVID-19 infection risks through aerosol transmission in supermarkets and small shops

Aerosol transmission is academically recognized as possible transmission route of Coronavirus disease 2019 (COVID-19). We established an approach to assess the airborne-disease infection risks through aerosol transmission based on the dose-response model and aerosol transport model. The accuracy of evaluation was guaranteed with on-site surveyed ventilation rate and occupant behavior. With the proposed approach, COVID-19 infection risks in 5 typical supermarkets and 21 small shops were evaluated. With one original infected early-shift staff, the average aerosols concentrations at steady-state are 1.06 × 10-3 RNA copies/m3 in the supermarkets and 4.73 × 10-2 RNA copies/m3 in the small shops. With the assumption of 5% original infected staff in the retail buildings, the infection probability of one customer is 1.40 × 10-6 for visiting one small shop and 6.22 × 10-6 for visiting one supermarket. The averaged infection risk in the supermarkets is higher than the small shops (p-value<0.001). On the other hand, the infection risks are higher for the staff working with the infected staff compared with the customers. The proposed approach can be applied to other occupied buildings and assist the pandemic control policy making for sustainable cities and society.