Effects of Air Filtration in COVID-19 Hospital Units

In areas where the COVID-19 pandemic has overwhelmed hospitals, makeshift COVID surge wards have had to be set up. Usually, these repurposed wards are not built for the isolation of patients with respiratory diseases and do not, e.g., have sufficient air exchange capabilities. Hospital-acquired COVID-19 cases, for example, in healthcare workers, can be a result.

Vilas Navapurkar, Cambridge University Hospitals NHS Foundation Trust, UK, and colleagues have investigated the effects of air filtration and sterilization using ultra-violet (UV) light on airborne SARS-CoV-2 and other microbes. The team studied two repurposed COVID-19 units in Cambridge, one surge ward with four beds and one surge intensive care unit (ICU) with five to six beds. They installed HEPA filter systems with UV sterilization in both units. They sampled the air in the units over one workweek with the filter systems inactive, then for one week with the systems running, and then again for a week with the filter systems turned off. PCR assays were used to detect the presence of SARS-CoV-2 and other microbes in the collected air samples.

The team found that in the non-intensive surge ward, airborne SARS-CoV-2 was detectable all throughout the first week in which the filter system was turned off. In the second week, when the filter system was running, no airborne SARS-CoV-2 was detected. When the system was kept turned off in the third week, the virus returned. In the surge ICU, SARS-CoV-2 was detected only infrequently throughout all three weeks. This could be due to a lower viral load in the upper respiratory tract in severely ill patients or the use of different respiratory devices. However, the prevalence of other airborne microbes was reduced in both the “normal” ward and the ICU setting when the filter systems were running.

Thus, portable air filtration devices could reduce the risk of exposure to respiratory pathogens such as SARS-CoV-2. They might improve the safety of repurposed “surge”-type facilities that are not well-equipped for isolation.

The removal of airborne SARS-CoV-2 and other microbial bioaerosols by air filtration on COVID-19 surge units,
Andrew Conway-Morris, Katherine Sharrocks, Rachel Bousfield, Leanne Kermack, Mailis Maes, Ellen Higginson, Sally Forrest, Joana Pereira-Dias, Claire Cormie, Tim Old, Sophie Brooks, Islam Hamed, Alicia Koenig, Andrew Turner, Paul White, R. Andres Floto, Gordon Dougan, Effrossyni Gkrania-Klotsas, Theodore Gouliouris, Stephen Baker, Vilas Navapurkar,
medRxiv 2021.
https://doi.org/10.1101/2021.09.16.21263684
The research has been published as a preprint and has not yet been peer-reviewed. It should not be used to guide clinical practice or health-related behavior.

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