A review of measurements of SARS-CoV-2 genetic material in air in outdoor and indoor environments: Implication for airborne transmission
This article was originally published here
Sci Total Approx. October 23, 2021: 151137. doi: 10.1016 / j.scitotenv.2021.151137. Online ahead of print.
The airborne transmission of SARS-CoV-2 has been the subject of debate in the scientific community since the start of the COVID-19 pandemic. This transmission mechanism could come from virus-laden aerosols released by infected individuals and is influenced by several factors. Among these, the concentration and particle size distribution of charged virus particles play an important role. Knowledge regarding aerosol transmission is increasing as new evidence is gathered in different studies, although there is not yet a standard protocol regarding air sampling and analysis, which can create challenges. difficulties in interpreting and applying the results. This work reports a systematic review of current knowledge gained from 73 published articles on the experimental determination of SARS-CoV-2 RNA in air by comparing different environments: outdoors, hospitals and indoor health facilities, and public community inside. Selected articles provided 77 datasets: outdoor studies (9/77, 11.7%) and indoor studies (68/77, 88.3%). Indoor data sets in hospitals were the vast majority (58/68, 85.3%) and the remainder (10/68, 14.7%) were classified as indoor community. The fraction of studies with positive samples, as well as the positivity rates (i.e. the ratios between positive and total samples) are significantly higher in hospitals compared to other typologies of sites. Contamination of surfaces was more common (in indoor data sets) compared to contamination of air samples; however, the average positivity rate was lower than that of air. SARS-CoV-2 RNA concentrations in air were highly variable and, on average, lower outdoors than indoors. Among interiors, concentrations in community interiors appear to be lower than in hospitals and healthcare facilities.