Respiratory Virus Deposition and Resuspension from Indoor Surfaces

Abstract

AbstractVirus-laden respiratory aerosols and droplets that are emitted during breathing, talking, coughing, and sneezing are removed from the indoor air via ventilation; filtration; deposition directly onto surfaces, such as clothing, furnishings, and floorings; and deposition onto dust present on these surfaces. The settled virus particles can be resuspended when they are disturbed via human activity or other external forces, such as strong air currents. The importance of resuspension as a transmission route for COVID-19 is unknown but was identified as a major research question during the 2020 US National Academies of Science, Engineering, and Medicine (NASEM) Airborne Transmission of SARS-CoV-2: A Virtual Workshop and remains an open question. Resuspended particles from human walking and other activities have been well characterized in the scientific literature and are known to play a large role in human inhalation exposure to many indoor pollutants. Based on preliminary estimates, the contribution of airborne SARS-CoV-2 virus is approximately 1/100 that of the direct emissions. Resuspension from clothing may play a more important role in exposure to viruses due to the closer proximity to the breathing zone. Further study is needed to confirm these preliminary results and better characterize resuspension of viruses in the indoor environment. Recommended mitigation measures to reduce exposure to resuspended particles indoors include reducing the initial viral particle emission into the indoor air via masks, reducing the concentration of airborne viral particles via ventilation and filtration, and reducing the loading of settled viral particles by maintaining clean surfaces.