SARS-CoV-2 Transmission Risk Reduction: Hopes and Failures

Reviewed by Cynthia T. Nguyen, PharmD; University of Chicago Medicine and Rebekah Moehring, MD, MPH; Duke University

As SARS-CoV-2 continues to spread, many people are searching for methods to reduce transmission and subsequent COVID-19 disease. Currently, social distancing and universal masking appear to be the most promising strategies. Though, household disinfectants and environmental factors have also been suggested to impact transmissibility and infection. However, data supporting these claims are limited and rapid uptake and reliance on these beliefs are not without risk.

SARS-CoV-2 may remain viable for hours to days on surfaces and cleaning and disinfection remains an important measure for the prevention of COVID-19. However, reports of an increasing number of calls to poison control centers related to exposures to disinfectants spurred the CDC to conduct a survey of knowledge and practice regarding household cleaning and disinfection. The survey revealed several gaps in knowledge, misperceptions, and risky practices involving household cleaners. Over one-third of respondents engaged in high-risk practices with intent of preventing the spread of SARS-CoV-2 including: washing food products with bleach, applying household cleaning or disinfectant products to bare skin, and intentionally inhaling or ingesting cleaners/disinfectants. One quarter (25%) of respondents reported at least one adverse health effect during the previous month that they believed had resulted from using cleaners or disinfectants, including: nose/sinus, skin, or eye irritation, dizziness, nausea, and breathing problems.

Inhalation of aerosolized particles has also been identified as an important route of transmission and loss of infectivity prior to inhalation may reduce the likelihood of aerosol transmission. An in vitro study sought to evaluate the effect of environmental factors on the stability of aerosolized SARS-CoV-2. In this study, environmentally controlled rotating drum aerosol chambers were used to expose aerosols containing SARS-CoV-2 to varying levels of humidity and simulated sunlight. Decay rates in simulated saliva were faster under simulated sunlight levels representing summer compared to late winter/early fall (90% loss in 6 minutes versus 19 minutes). The decay rate was similar across all humidity levels evaluated (90% loss in 125 minutes), in the absence of simulated sunlight. These findings suggest that exposure risk with aerosolized SARS-CoV2 may be reduced by sunlight, but not humidity. Variations in temperature were not evaluated. Though promising, additional studies are needed in order to understand how these findings will translate into daily activities.

As strategies to reduce transmission are increasingly studied, in vitro data must be interpreted cautiously. Furthermore, efforts to ensure appropriate and accurate public messaging may be need to optimize safe prevention practices and prevent harm in the time of COVID-19.


  1. Schuit M, Ratnesar-Shumate S, Yolitz J, et al. Airborne SARS-CoV-2 is Rapidly Inactivated by Simulated Sunlight [published online ahead of print, 2020 Jun 11]. J Infect Dis. 2020;jiaa334. doi:10.1093/infdis/jiaa334
  2. Gharpure R, Hunter CM, Schnall AH, et al. Knowledge and Practices Regarding Safe Household Cleaning and Disinfection for COVID-19 Prevention — United States, May 2020. MMWR Morb Mortal Wkly Rep 2020;69:705–709. 
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