HEPA purifiers not tied to less viral exposure in elementary classrooms, analysis finds

A secondary analysis of a randomized clinical trial involving 200 elementary school classrooms in the U.S. found that the use of portable high-efficiency particulate air (HEPA) purifiers was associated with a modest reduction in respiratory virus diversity, though it did not decrease overall viral exposure. The study, published on October 6, 2023, in JAMA Network Open, was led by researchers from Boston Children’s Hospital and examined data collected between September 2015 and June 2020 across 39 public schools in the Northeast.

Classrooms were randomly assigned to either receive four active HEPA purifiers or four identical filterless units. The researchers analyzed week-long bioaerosol samples and measured the presence of 19 respiratory viruses using digital droplet polymerase chain reaction (ddPCR). The primary focus was on high viral exposure, with secondary outcomes including viral diversity and individual virus levels.

Results indicated that HEPA purifiers did not effectively lower the total viral load in classrooms. The study revealed that viruses were detected in 98.5% of analyzed samples, with the most common being rhinovirus. Environmental factors influencing viral exposure included low humidity and increased levels of particulate matter.

The authors emphasized the need for further research into comprehensive environmental interventions to manage viral exposure in school settings.