Measurement of Airborne Virus (Influenza A) Concentration before and after Resuspension Activity

MAHENDER SINGH RAWAT, Andrea Ferro, Clarkson University

     Abstract Number: 647
     Working Group: Aerosol Science of Infectious Diseases: What We Have Learned and Still Need to Know about Transmission, Prevention, and the One Health Concept

Abstract
Many respiratory viruses, including influenza and COVID-19, are transmitted via the emission and inhalation of infectious respiratory aerosols in indoor environments. Resuspended particles from the surfaces can be a major source of airborne microbiological contaminants in indoor environments; however, it is unknown whether resuspended viruses contribute substantially to disease transmission. In this study, we investigated the resuspension of influenza A virus x31 H3N2 strain (7 ml of phosphate buffered saline with 109 virus stock), which was generated through a nebulizer into a sealed biosafety level 2 laboratory. After allowing the particles to settle on the floor and other surfaces for several hours, an investigator entered the room to resuspend the particles via 15 minutes of human walking activity. Air samples were collected during the emission and resuspension periods using the impingers, and surface samples were collected using swabs and petri dishes. An array of optical particle counters (Purple Air) and an aerodynamic particle sizer (TSI model 3321) were used to continuously measure the particle concentration in the room during the experiments. We used RT-PCR to measure the viral load collected in the impingers and surface samples. The viral load following the resuspension events were approximately two orders of magnitude lower than that following direct emission via the nebulizer. Thus, depending on the infectious dose and viability of a particular virus, resuspension of settled respiratory viruses could lead to transmission, but the risk appears to be much lower than for direct emission. Due to a higher intake fraction (fraction of emitted particles that are inhaled), resuspension of virus particles from clothing could be more important than resuspension from flooring during human activity.

Key words: resuspension, Influenza, virus, transmission, indoor aerosols