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Aerosol generating procedures: are they of relevance for transmission of SARS-CoV-2?

Press release issued: 7 May 2021

Emerging evidence indicates that many currently defined aerosol generating procedures (AGPs) are unlikely to play any significant role in the generation of infectious aerosol that poses a risk to hospital staff. In a comment article published in The Lancet Respiratory Medicine today [6 May] a research team from the University of Bristol discusses AGPs and the transmission of SARS-CoV-2 in a healthcare setting.

Current UK infection control guidance for hospitals is centred on the basis that aerosols are only generated by specific medical interventions described as aerosol generating procedures (AGPs).

The comment article suggests it is becoming increasingly clear that transmission of SARS-CoV-2 via aerosol is possible and might represent a significant transmission route. However, emerging evidence indicates that many currently defined AGPs are unlikely to play any significant role in the generation of infectious aerosol that poses a risk to staff.

More research is ongoing to measure other AGPs across a range of clinical settings. However, based on the research to date, a coughing patient with acute COVID-19 is likely to generate more infectious aerosol than many AGPs. This appears to be supported by the epidemiological evidence, which points to an increased risk of infection for ward medical staff (who care for patients who have difficulty in breathing and coughing patients with COVID-19) compared with intensive care staff — although there is some limitation to the  interpretation of that data such as patient mix, among other factors.

In light of this evidence, the researchers propose an end to the term aerosol generating procedure and instead focus should be on the risk in plain sight: close, physical exposure to people suspected, or known to have, COVID-19 for prolonged time or where ventilation remains poor.

Nick Maskell, Professor of Respiratory Medicine at the Academic Respiratory Unit and Bristol Medical School: Translational Health Sciences (THS), said: “We propose that clinicians follow an evidence-based framework that accounts for the major sources of risk, with a focus on physical exposure to patients with suspected or confirmed COVID-19 as the critical component.

“Additional factors known to be relevant in viral transmission, such as ventilation, proximity, and the length time of exposure to patients, should be included in assessing risk, while recognising the changing epidemiology of infection with setting.”


'Aerosol generating procedures: are they of relevance for transmission of SARS-CoV-2?' by Fergus Hamilton, David Arnold, Bryan R Bzdek, James Dodd, AERATOR group, Jonathan Reid, Nick Maskell in The Lancet Respiratory Medicine

Further information

About the North Bristol Lung Centre, Academic Respiratory Unit (ARU)
The Academic Respiratory Unit, led by Professor Nick Maskell, is based at the Learning and Research Building at Southmead Hospital. We design, lead and deliver research into a wide range of respiratory conditions, with a particular focus on clinical studies and trials. Our unit has particular interests in pleural disease, airways diseases such as asthma and COPD, and interstitial lung disease.

About the Bristol Aerosol Research Centre (BARC)
Research at the Bristol Aerosol Research Centre (BARC) is focussed on improving our understanding of the physical and chemical properties of aerosols at a single particle level. Aerosols play important roles in a broad range of disciplines including atmospheric science, the delivery of drugs to the lungs, the formation of structured micro- and nanoparticles, and combustion science.

Bristol UNCOVER Group
In response to the COVID-19 crisis, researchers at the University of Bristol formed the Bristol COVID Emergency Research Group (UNCOVER) to pool resources, capacities and research efforts to combat this infection.

Bristol UNCOVER includes clinicians, immunologists, virologists, synthetic biologists, aerosol scientists, epidemiologists and mathematical modellers and has links to behavioural and social scientists, ethicists and lawyers.

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For more information about the University of Bristol’s coronavirus (COVID-19) research priorities visit:

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