Some public places may need better ventilation to prevent the spread of covid-19 after growing evidence of the disease’s “long-distance” airborne transmission potential, suggests research published today by The BMJ.
A review of 18 existing studies indicates that airborne transmission of the SARS-CoV-2 virus from an infectious person to others located more than two meters away may occur in different indoor non-health environments.
However, the researchers stress that the evidence from these studies was considered of very low certainty and say that further research on the long-range airborne transmission potential of SARS-CoV-2 is needed.
Since the early stages of the covid-19 pandemic and so-called “superpropagator” events, there has been growing evidence to suggest that airborne transmission of the SARS-CoV-2 virus in poorly ventilated areas has helped spread the infection.
It is generally accepted that short-range transmission (less than two meters away) can occur through both droplets and aerosols in the air, but there is a lack of agreement on the importance of long distance air transmission (more than two meters) in indoor environments. such as hotel premises, leisure facilities, workplaces or apartment blocks.
Therefore, a team of researchers from the UK Health Safety Agency and the University of Bristol set out to assess the potential for long-range airborne transmission of SARS-CoV-2 in indoor community settings and to investigate the factors that they could influence transmission.
They reviewed studies on the subject published between January 2020 and January 2022, focusing on 18 observational studies of covid outbreaks in countries in Asia, Europe, Oceania and the US.
These outbreaks occurred in a variety of community settings, such as apartment block flats, quarantine hotels, restaurants, buses, a food processing factory, a courtroom, a gym, and during singing events.
The authors of the review concluded that long-distance air transmission was likely to have occurred for some or all of the transmission events in 16 of 18 studies. In the other two studies it was not clear.
In all 16 studies, one or more factors are likely to have increased the odds of long-distance air transmission, especially insufficient air replacement, directional airflow, and activities associated with increased air emission. ‘aerosols, such as singing or speaking aloud.
In 13 studies, individuals who could be the source of infection were reported to be asymptomatic, pre-symptomatic, or just beginning to have symptoms at the time of transmission.
The review has some limitations, for example, it only analyzed epidemiological observational studies of people-to-people transmission events in the real world and did not include broader evidence from environmental or experimental studies.
In addition, most outbreaks occurred prior to vaccine release and it is unclear how these results are applied to populations with a high level of immunity to infection, either acquired naturally or mediated by the vaccine. .
However, the review critically assessed the likelihood of long-range airborne transmission of SARS-CoV-2 using a range of evidence from epidemiological data, genomic analysis, and video surveillance to seat layout analysis. and environmental hypothesis testing.
As such, the authors conclude: this rapid systematic review demonstrates the existing evidence that long-range airborne transmission of SARS-CoV-2 can occur in indoor environments, such as restaurants, workplaces, and places for hearts, and identified factors such as insufficient air replacement. which can contribute to transmission.
“These results support the role of mitigation measures in indoor environments, such as adequate ventilation,”
Now is the time for an indoor air revolution, argues Stephanie Dancer, a consulting microbiologist at Napier University in Edinburgh, in a linked editorial.
He also points out some limitations of the study, but says that “the evidence presented in this review, however faint, validates the premise that tiny respiratory particles containing SARS-CoV-2 are freely transmitted through environments with inadequate ventilation. .
Public health leaders are expected to develop practical guidelines and “tilt” people and places closer to safety. “
Stephanie Dancer, consulting microbiologist, Napier University of Edinburgh
Source:
Magazine reference:
Duval, D., et al. (2022) SARS-CoV-2 long-range airborne transmission: rapid systematic review. The BMJ. doi.org/10.1136/bmj-2021-068743.