Sampling and Detection of Sars-Cov-2 Aerosol in Well and Poorly Ventilated Places and Its Exposure Risks: A Review of Field Sampling Studies

YUETONG ZHANG, Sripriya Nannu Shankar, William Vass, John Lednicky, Z. Hugh Fan, Duzgun Agdas, Chang-Yu Wu, University of Florida

     Abstract Number: 644
     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
As SARS-CoV-2 continuously sweeps throughout the globe, the White House Office of Science and Technology Policy (OSTP) and other federal agencies have collaborated together to introduce the Clean Air in Buildings Challenge, which emphasizes better ventilation, filtration, and air disinfection. Data from 30 SARS-CoV-2 field sampling studies from the literature, including isolation homes (9) and hospitals (25), were compiled to assess whether better ventilation leads to lower exposure risk. Air changes per hour (ACH) was used as a surrogate for ventilation. The concentration of virus RNA in air (quantified by RT-PCR) and the percentage of air samples that tested positive for SARS-CoV-2 (positivity rate) were used to inform exposure risk. The ACH values were averaged across hospitals and isolation homes, respectively, and the ACH for each hospital was averaged over all room types. The mean ACH was higher in hospitals (10.6) compared to isolation homes (1.4). The mean positivity rate was calculated across hospitals and homes, respectively. The positivity rate in hospitals (24.1%) was moderately lower compared to that in isolation homes (38.0%). The virus RNA concentration was averaged across all air samples at hospitals and homes, respectively. The mean concentration of SARS-CoV-2 RNA in hospital settings (102 copies/L) was significantly lower compared to that in isolation homes (1.9*10⁷ copies/L). While a larger sample size and more consistent sampling protocols (e.g., placement of the sampler, type of sampler, primer used, and sampling duration) will reduce uncertainty, our analysis illustrates that the exposure risk of SARS-CoV-2 is higher in isolation homes compared to hospital rooms, and a higher ventilation rate can reduce the exposure risk.