Airborne SARS-CoV-2 Is Rapidly Inactivated by Simulated Sunlight

Abstract Aerosols represent a potential transmission route of COVID-19. This study examined effect of simulated sunlight, relative humidity, and suspension matrix on stability of SARS-CoV-2 in aerosols. Simulated sunlight and matrix significantly affected decay rate of the virus. Relative humidity alone did not affect the decay rate; however, minor interactions between relative humidity and other factors were observed. Mean decay rates (± SD) in simulated saliva, under simulated sunlight levels representative of late winter/early fall and summer were 0.121 ± 0.017 min−1 (90% loss, 19 minutes) and 0.306 ± 0.097 min−1 (90% loss, 8 minutes), respectively. Mean decay rate without simulated sunlight across all relative humidity levels was 0.008 ± 0.011 min−1 (90% loss, 286 minutes). These results suggest that the potential for aerosol transmission of SARS-CoV-2 may be dependent on environmental conditions, particularly sunlight. These data may be useful to inform mitigation strategies to minimize the potential for aerosol transmission. This study demonstrates that simulated sunlight rapidly inactivates SARS-CoV-2 in small-particle aerosols, suggesting that exposure risk may vary significantly across different environmental conditions.