Research by an Australian respiratory specialist shows how important ventilation and air filters are in the fight against COVID-19.
Dr Simon Joosten received a $50,000 scholarship from the Epworth Medical Foundation to further his research into the use of HEPA filters to improve ventilation in hospitals.
He said air filtration was a "massive blind spot" in healthcare before the COVID-19 pandemic swept the globe.
"We know that some lung infections are transmitted by the air - notably tuberculosis, which has been around for a long time, and that only transmits via the air," Dr Joosten said.
"Most of talk around infection control focuses on touch, or droplets like sneezing.
"And from the mid-19th century in the US, any research or talk about viruses being transmitted via the air was really squashed and people who believed in that were called 'miasma theorists'.
"In the 1950s we learned that aerosols stay in the air, they can be inhaled into the lungs and depending on their size, they can get to the bottom of your lungs.
"We now know that aerosols that are 100 microns in size stay airborne for a long time. And when COVID hit, we were really blindsided and it took the World Health Organization and the Centres for Disease Control until April 2021 to acknowledge that COVID is airborne."
For most of 2020, Dr Joosten added, "we weren't mitigating against aerosol transmission".
"If you are in an environment like a COVID ward, even wearing an N95 mask and there's no ventilation you will get COVID infiltration into your nose - we can trace it," he said.
"But if you add ventilation, on top of the N95 mask, there's no infiltration. So, wearing PPE and an N95 mask helps, but it's not enough."
Dr Joosten's study, which is under peer review, has already guided changes to hospital ventilation at Epworth Richmond in Melbourne.
Epworth HealthCare's Group Chief Executive, Dr Lachlan Henderson, said keeping patients, staff and doctors safe had been the priority throughout the pandemic.
"Epworth has implemented a higher level of PPE across key areas such as our emergency departments, intensive care units and COVID-19 ward," Dr Henderson said.
"We have also regularly reviewed airflows at each of our hospitals.
"Dr Joosten's virus aerosol research was critical in guiding our infection control team to deploy HEPA filter technology at Epworth, as additional protection to keep our hospitals safe."
The research has also made a difference outside the hospital.
"We presented our findings to the Victorian government, and they immediately spent $190 million on HEPA filters for classrooms," Dr Joosten said.
"It's a cost-effective way of controlling transmission - re-engineering buildings is expensive and often not possible.
"These air filters stop that gap. Here in Victoria, we have learned the hard way how to deal with COVID.
"And from a variant point of view, there's no variant that cannot be blocked by a HEPA filter. The filters take variants out of the equation."
Dr Joosten said HEPA filters could also be used in homes and offices.
"Australians spend 90 percent of their time inside and there are no regulations regarding air quality inside buildings.
"It's a massive gap - there's just no overarching regulations requiring monitoring of air quality," he said.
"People can buy HEPA filters on Amazon and they're very effective. We used an off-the-shelf one during the research and it works really well."
As the pandemic continues, Dr Joosten said it was vital to protect frontline workers.
"Our study highlights the need to provide multiple layers of protection to healthcare workers during the COVID-19 pandemic," he said.
"Among the most important protective measures are vaccination, personal protective equipment and ventilation. Our study shows personal protective equipment and ventilation interact to provide added protective benefits against virus-laden aerosols."
Dr Joosten's research can be found online at PubMed and medRxiv.
