An air filtration machine placed on a Covid-19 hospital ward removed almost all traces of the SARS-CoV2 coronavirus, according to a new study by researchers at the University of Cambridge in the U.K.
“Reducing airborne transmission of the coronavirus is extremely important for the safety of both patients and staff,” said Vilas Navapurkar, MD, a Consultant in Intensive Care Medicine at Cambridge University Hospitals and leader of the study. “Effective personal protective equipment has made a huge difference, but anything we can do to reduce the risk further is important,” Navapurkar added.
The U.K. experienced very high levels of Covid-19 hospitalizations earlier on in the pandemic, stretching the capabilities of the National Health Service. As part of this, hospital wards not normally used for patients with infectious diseases or respiratory diseases were often used to cope with numbers of patients and the study was in part inspired by the need to make these spaces safer for patients and staff.
“Because of the numbers of patients being admitted with Covid-19, hospitals have had to use wards not designed for managing respiratory infections. During an intensely busy time, we were able to pull together a team from across the hospital and University to test whether portable air filtration devices, which are relatively inexpensive, might remove airborne SARS-CoV-2 and make these wards safer,” said Navapurkar.
The team installed filtration devices containing High Efficiency Particulate Air (HEPA) devices with UV sterilization on two types of surge wards, one with patients requiring fairly minor treatment such as oxygen and the other, a full intensive care unit with patients requiring more substantial respiratory support, such as ventilators. The air filtration machines were operated continuously for one week and filtered the air in each room between 5-10 times per hour.
The researchers also developed a new technique for sampling air, then analyzing it using a PCR assay for traces of virus, similar to the nasal-sampling Covid-19 tests which are currently used around the world.
On the surge ward with patients requiring moderate support such as oxygen, the SARS-CoV2 virus could be detected consistently before the air filtration unit was switched on, but not on any of five testing days afterwards. After switching off the machine, the researchers once again were able to detect airborne virus.
“We were really surprised by quite how effective air filters were at removing airborne SARS-CoV-2 on the wards,” said first author Andrew Conway Morris, MD, PhD, from the Department of Medicine at the University of Cambridge. “Although it was only a small study, it highlights their potential to improve the safety of wards, particularly in areas not designed for managing highly infectious diseases such as Covid-19,” added Conway Morris.
On the ICU ward, the results were less clear, with the researchers unable to find much airborne SARS-CoV2 on the days before the machine was switched on and detecting trace amounts on one day when the filtration was active. However, the team also found that the air filters reduced levels of fungal and bacterial bioaerosols as well as those of other viruses on both wards tested, reducing the overall number of pathogens in the air.
After a heap of slightly bizarre controversy and in tandem with a growing mountain of evidence indicating the SARS-CoV2 virus is airborne, the World Health Organization finally updated its guidance in May to confirm that this is indeed the case and is likely to be a dominant method by which the virus is transmitted. Slowly, but surely public health departments around the world are increasingly recommending improvements in ventilation and air filtration to minimize the risk of virus transmission in enclosed environments, not just within healthcare settings but in any indoor environment where people gather, such as restaurants, bars, gyms and private homes.
“We’re all familiar with the idea of having standards for clean water and of hygiene standards for food. We need now to agree standards for what is acceptable air quality and how we meet and monitor those standards,” said Navapurkar.