Excerpt by Dong Gao
“The influence of temperature, humidity, and simulated sunlight on the infectivity of SARS-CoV-2 in aerosols”
Paul Dabisch, Michael Schuit, Artemas Herzog, Katie Beck, Stewart Wood, Melissa Krause, David Miller, Wade Weaver, Denise Freeburger, Idris Hooper, Brain Green, Gregory Williams, Brain Holland, Jordan Bohannon, Victoria Wahl, Jason Yolitz, Michael Hevey & Shanna Ratnesar-Shumate
Read the full article: Aerosol Science and Technology, 55:2, 142-153, DOI: 10.1080/02786826.2020.1829536
A person infected with COVID-19 releases viral material in the form of ballistic droplets when they cough or shout, as well as smaller-sized aerosols through other respiratory activities such as breathing, speaking or singing. A recent study by Dabisch et al. reports the influence of different environmental conditions on the infectivity of SARS-CoV-2 in aerosols. In this work, SARS-CoV-2 was aerosolized and introduced into an environmentally controlled rotating drum. Virus-laden aerosols were sampled periodically onto gelatin filters, and the viral infectivity was evaluated in vitro on cell culture using a microtitration infectivity assay across a wide range of temperatures (from 10 ℃ to 40 ℃), relative humidity levels (20% to 70%), and simulated sunlight levels (darkness to 1.9W/m² integrated UVB).
Although the infectious dose in humans is not known, this study demonstrates SARS-CoV-2 remained viable in aerosols for hours, depending on the environmental conditions. While all factors investigated in this study were found to influence the persistence of infectious virus in aerosol, SARS-CoV-2 was more susceptible to sunlight than heat or relative humidity. The virus was more stable in darkness but lost 90% of infectivity within a few minutes when exposed to simulated sunlight representative of noon on a clear summer day, suggesting that persistence and subsequent exposure risks may vary significantly between indoor and outdoor environments. This study suggests that adequate control of the environmental factors and proper human behavior in accordance with the environmental conditions may be useful to mitigate COVID-19 risks associated with airborne transmission.
Figure 1. Decay constants for viral infectivity as a function of temperature and humidity (a) in darkness and (b) at 1.9 W/m2 UVB irradiance.