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. 2022 Feb 25:809:151137.
doi: 10.1016/j.scitotenv.2021.151137. Epub 2021 Oct 23.

A review on measurements of SARS-CoV-2 genetic material in air in outdoor and indoor environments: Implication for airborne transmission

Adelaide Dinoi  1 , Matteo Feltracco  2 , Daniela Chirizzi  3 , Sara Trabucco  4 , Marianna Conte  5 , Elena Gregoris  2 , Elena Barbaro  2 , Gianfranco La Bella  3 , Giuseppina Ciccarese  3 , Franco Belosi  4 , Giovanna La Salandra  3 , Andrea Gambaro  6 , Daniele Contini  7
Affiliations

A review on measurements of SARS-CoV-2 genetic material in air in outdoor and indoor environments: Implication for airborne transmission

Adelaide Dinoi et al. Sci Total Environ. .

Abstract

Airborne transmission of SARS-CoV-2 has been object of debate in the scientific community since the beginning of COVID-19 pandemic. This mechanism of transmission could arise from virus-laden aerosol released by infected individuals and it is influenced by several factors. Among these, the concentration and size distribution of virus-laden particles play an important role. The knowledge regarding aerosol transmission increases as new evidence is collected in different studies, even if it is not yet available a standard protocol regarding air sampling and analysis, which can create difficulties in the interpretation and application of results. This work reports a systematic review of current knowledge gained by 73 published papers on experimental determination of SARS-CoV-2 RNA in air comparing different environments: outdoors, indoor hospitals and healthcare settings, and public community indoors. Selected papers furnished 77 datasets: outdoor studies (9/77, 11.7%) and indoor studies (68/77. 88.3%). The indoor datasets in hospitals were the vast majority (58/68, 85.3%), and the remaining (10/68, 14.7%) were classified as community indoors. The fraction of studies having positive samples, as well as positivity rates (i.e. ratios between positive and total samples) are significantly larger in hospitals compared to the other typologies of sites. Contamination of surfaces was more frequent (in indoor datasets) compared to contamination of air samples; however, the average positivity rate was lower compared to that of air. Concentrations of SARS-CoV-2 RNA in air were highly variables and, on average, lower in outdoors compared to indoors. Among indoors, concentrations in community indoors appear to be lower than those in hospitals and healthcare settings.

Keywords: Airborne transmission; COVID-19; Indoor; Outdoor; SARS-CoV-2 in air.

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Conflict of interest statement

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Unlabelled Image
Graphical abstract
Fig. 1
Fig. 1
Flowchart of the identification, screen, and assessment of the records included in this review according to PRISMA statement (Page et al., 2021).
Fig. 2
Fig. 2
Geographical distribution of the 73 studies included in this review.
Fig. 3
Fig. 3
Number of datasets reviewed for the different typologies of sites. Negative indicates dataset with all air samples that gave negative results for the presence of SARS-CoV-2 and positive indicates the datasets in which at least one of the air samples tested positive.
Fig. 4
Fig. 4
Positivity rates as function of the total number of samples collected for the different datasets having positive samples collected in hospitals, care facilities, and quarantine areas. (a) refers to air samples; (b) refers to surface (swab) samples; (c) comparison of frequency distributions of positivity rates for the datasets of air and surface samples collected in hospital and care facilities. Red continuous lines represent the minimum positivity rate (i.e. one positive sample) as a function of the total number of samples. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 5
Fig. 5
Frequency distribution of SARS-CoV-2 concentrations measured in air samples in the different datasets referring to hospital and care facilities sites.
See this image and copyright information in PMC

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