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

Abstract

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.

Keywords: COVID-19; infection risk; public health; quantitative microbial risk assessment; retail building.

Fig. 1

Infection risk assessment approach: (a) dose-response theory; and (b) steps of infection risk assessment.

Fig. 2

Removal rate of aerosols: (a) Filtration removal rate; (b) Surface deposition rate; (c) Total removal rate.

Fig. 3

Variation of viral aerosol concentrations in the 1^st supermarket: (a) the infected staff is on early shift; and (b) the infected staff is on late shift.

Fig. 4

Variation of viral aerosol concentration in 1^st small shop: (a) infected staff is on early shift; and (b) infected staff is on late shift.

Fig. 5

Steady-state virus concentrations in the retail buildings: (a) supermarkets; and (b) small shops.

Fig. 6

Inhaled virus dose by the staff: (a) supermarket; and (b) small shops.

Fig. 7

Inhaled virus by the customers: (a) supermarket; and (b) small shops.

Fig. 8

Infection probability of the susceptibles with one infected early-shift staff: (a) customers; (b) early-shift staff; and (c) late-shift staff.

Fig. 9

Sensitivity analysis results with Sobol's method: (a) one-order sensitivity index; and (b) total sensitivity index.