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October 11, 2021 – High-efficiency particulate air (HEPA) filters and ultraviolet (UV) light sterilization effectively remove SARS-CoV-2 particles from the air – the first such evidence in real-world test, researchers report in the medRxiv server preprint.
The journal Nature reported this week that research, which has not been peer-reviewed, suggests that filters may help reduce the risk of hospital-acquired SARS-CoV-2.
Researchers, led by intensivist Andrew Conway-Morris ,, PhD, with the Division of Anesthesia at the School of Clinical Medicine at the University of Cambridge, UK, write that previous experiments evaluated the capacity of filters of air to remove inactive particles in carefully controlled environments, but it was not known how they would work in a real-world environment.
Co-author Vilas Navapurkar, MBChB, an ICU doctor at Addenbrooke Hospital in Cambridge, UK, said hospitals used portable air filters when facilities of their insulation are complete, but evidence was required as to whether these filters were effective or whether they provided a false sense of security.
The researchers installed the filters in two fully occupied COVID-19 halls – a general hall and an ICU. They chose HEPA filters because they can trap very small particles.
The team collected air samples from the wards during one week when the air filters were turned on and two weeks when they were turned off, then compared the results.
According to the study, “SARS-CoV-2 in the air was detected in the ward in all five days prior to activation of the air / UV filtration, but in none of the five days when the an air / UV filter was operational; SARS-CoV-2 was found again in four to five days when the filter was switched off. “
SARS-CoV-2 in the air was not often found in the ICU, even when the filters were turned off.
Cheap and Easy
According to Nature article, the authors suggest several potential explanations for this, “including slower viral replication in later stages of the disease.” Therefore, the authors say, virus filtration from the air may be more important in general wards than in ICUs.
Filters significantly reduced other microbial bioerosols both in the ward (48 pathogens detected before filtration, 2 after) and in the ICU (45 pathogens detected before filtration, 5 after).
The National Institute for Occupational Health and Safety (NIOSH) cyclonic aerosol samplers and PCR tests were used to detect SARS-CoV-2 in the air and other microbial bioerosol .
David Fisman, MD, an epidemiologist at the University of Toronto, Canada, who was not involved in the research, said in Nature “This study suggests that HEPA air cleaners, which remain little used in Canadian hospitals, are a cheap and easy way to reduce the risk of airborne pathogens.”
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