COVID-19 has created major challenges for patients, hospitals and wider society since it first emerged in late 2019. The large numbers of patients admitted to hospitals have overwhelmed respiratory isolation facilities. In the early stages of the pandemic, modes of transmission were uncertain, with considerable focus on droplet and fomite based prevention strategies. As experience was gained it has become increasingly apparent that aerosol-based transmission is a major route for both near and far-field transmission, and is not restricted to ‘aerosol-generating procedures’.

Our group has investigated the ability of air purification to improve the safety of air in surge units used to manage patients with COVID.

In a cross-over design study we found SARS-CoV-2 in the air of a ward managing patients with COVID-19, mostly in small (1-4micron) particles. When we turned on an air purification device (combined HEPA filter with UV irradiator) SARS-CoV-2 became undetectable, but was again detectable when the filter was turned off. We found a wide range of other bioaerosols including fungi, bacteria and other viruses in the air, which were also substantially reduced by the use of the air purifier. Interestingly, in a surge covid ICU we did not find airborne SARS-CoV-2 but did see a similar reduction in other bioaersol when the air purifier was activated.

We conclude that air purification may play a role in reducing nosocomial COVID transmission, with potential for wider impact on other nosocomial infections in vulnerable patients.