Research progress on the infection risk of SARS-CoV-2 by environmental transmission

Objective The emerging new variants of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) continue to attract wide attention.A literature review on the infection risk of SARS-CoV-2 through environmental transmission will help understand its transmission mechanism.

Methods Focusing on mathematical modeling, animal modeling, and environmental surveillance methods, relevant literature was searched to review the risk of SARS-CoV-2 transmission via different routes.

Results A total of 19 847 articles met the search criteria, among which 60 studies were included in this review.Mathematical modeling studies revealed that the transmission risk of SARS-CoV-2 was the highest via droplets, followed by aerosols, and finally via contact.Wearing masks and indoor ventilation could effectively reduce the risk of SARS-CoV-2 infection.Animal experiments when ferrets and hamsters were used as research objects showed that approximately 82% of susceptible animals could be infected via airborne transmission (including aerosol and droplet transmission), which could be the major transmission route for SARS-CoV-2.According to environmental monitoring research, SARS-CoV-2 could be detected on some surfaces of critical items, generally at low concentrations, and the infection risk for a single indirect contact was estimated using quantitative microbial risk assessment to be as low as 1 in 10 000.

Conclusion Compared with indirect contact, airborne transmission is more likely to be the main transmission route of SARS-CoV-2.