Abstract
Background: Airborne transmission is the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in the air. We carried out a systematic review to identify, appraise and summarise the evidence from studies of the role of airborne transmission of SARS-CoV-2. Methods: We searched LitCovid, MedRxiv, Google Scholar and the WHO Covid-19 database from 1 February to 20 December 2020 and included studies on airborne transmission. Data were dual extracted and we assessed quality using a modified QUADAS 2 risk of bias tool. Results: We included 67 primary studies and 22 reviews on airborne SARS-CoV-2. Of the 67 primary studies, 53 (79%) reported data on RT-PCR from air samples, 12 (18%) report cycle threshold values and 18 (127%) copies per sample volume. All primary studies were observational and of low quality. The research often lacked standard methods, standard sampling sizes and reporting items. We found 36 descriptions of different air samplers deployed. Of the 42 studies conducted in-hospital that reported binary RT-PCR tests, 24 (57%) reported positive results for SARs-CoV-2 (142 positives out of 1,403 samples: average 10.1%, range 0% to 100%). There was no pattern between the type of hospital setting (ICU versus non-ICU) and RT-PCR positivity. Seventeen studies reported potential air transmission in the outdoors or in the community, of which seven performed RT-PCR sampling, and two studies reported weak positive RNA samples for 2 or more genes (5 of 125 samples positive: average 4.0%). Ten studies attempted viral culture with no serial passage. Conclusion: SARS-CoV-2 RNA is detected intermittently in the air in various settings. Standardized guidelines for conducting and reporting research on airborne transmission are needed. The lack of recoverable viral culture samples of SARS-CoV-2 prevents firm conclusions from being drawn about airborne transmission.
Highlights
Airborne transmission is defined as the spread of an infectious agent caused by the dissemination of droplet nuclei that remain infectious when suspended in air over long distances and time For this definition of airborne transmission, emerging discussion has suggested aerosol transmission occurs in both short- and long-range.Response: Our definition was based on current World Health Organization (WHO) guidance
We are undertaking a series of living systematic reviews investigating factors and circumstances that impact the transmission of SARS-CoV-2, based on our published protocol last updated on 1 December 2020 Briefly, this review aims to identify, appraise, and summarize the evidence relating to the role of airborne transmission of SARS-CoV-2 and the factors influencing transmissibility
There is a current lack of well-conducted studies addressing airborne transmission: only nine studies identified during the search period reported air sampling outdoors and, in the environment, outside of hospitals
Summary
Airborne transmission is defined as the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in air over long distances and time For this definition of airborne (aerosol) transmission, emerging discussion has suggested aerosol transmission occurs in both short- and long-range (see my review).Response: Our definition was based on current WHO guidance. Airborne transmission is defined as the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in air over long distances and time For this definition of airborne (aerosol) transmission, emerging discussion has suggested aerosol transmission occurs in both short- and long-range (see my review). “Airborne transmission is defined as the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in air over long distances and time.[1] some authors have defined aerosol transmission as occurring over both short and long distances ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7982882/).”. Airborne transmission is the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in the air. Data were dual extracted and we assessed quality using a modified QUADAS 2 risk of bias tool.
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