Real-world data shows filters clean COVID-causing virus from the air

Research at a hospital flooded with people with COVID-19 confirmed that portable air filters effectively remove SARS-CoV-2 particles from the air – the first such evidence in a real environment¹. The results suggest that air filters could be used to reduce the risk of patients and medical staff contracting SARS-CoV-2 in hospitals, according to the study’s authors.

Despite the proper use of personal protective equipment, hospitals have reported a significant spread of SARS-CoV-2 from patients to health workers. One of the suspected causes of such cases is virus particles in the air, which is one of the main drivers of transmission of SARS-CoV-2.

Previous experiments that tested the performance of air filters evaluated their ability to remove inactive particles while operating in carefully controlled environments.². As a result, “what was not known was how effective they would be in a real world service in eliminating SARS-CoV-2,” says study co-author Vilas Navapurkar, a doctor in the intensive care unit (ICU) in Addenbrooke. Cambridge Hospital, UK. Hospitals have turned to portable air filters as an attractive solution when their isolation facilities are full, Navapurkar says, but it is important to know whether these filters are effective or whether they simply provide a false sense of security.

To determine how the filters withstand real-world conditions, Navapurkar and his co-authors installed them in two fully occupied COVID-19 wards – a general ward and an intensive care unit. The team chose High Efficiency Particulate Filters (HEPA), which blow air through a fine mesh that traps extremely small particles. The researchers collected air samples in the wards for a week when the air filters were on and two weeks when they were off.

In general duty, the team found particles of SARS-CoV-2 in the air when the filter was off but not when it was on. Surprisingly, the team didn’t find many virus particles in the air in the intensive care unit, even with the filter turned off. The authors suggest several possible reasons for this, including slower viral replication in later stages of the disease.³. As a result, the team says measures to remove the virus from the air could be more important in general wards than in intensive care units.

A simple solution

“This study suggests that HEPA air purifiers, which remain little used in Canadian hospitals, are a simple and inexpensive way to reduce the risks associated with airborne pathogens,” said David Fisman, epidemiologist at the University of Toronto, Canada, which was not involved. in the search.

And scientists have found that filters don’t just protect against SARS-CoV-2. When the filters were turned off, the air in both wards contained detectable amounts of other pathogens that cause infections in hospitals, such as Staphylococcus aureus, Escherichia coli and Pyogenic streptococcus. Filters have largely removed them. These organisms are generally not thought to spread through the air, but “this study suggests that these infections can also be spread by aerosol,” says Fisman.

The findings have yet to be peer reviewed.