HEPA filters of portable air cleaners as a tool for the surveillance of SARS-CoV-2.

Studies about the identification of SARS-CoV-2 in indoor aerosols have been conducted in hospital patient rooms and to a lesser extent in nonhealthcare environments. In these studies, people were already infected with SARS-CoV-2. However, in the present study, we investigated the presence of SARS-CoV-2 in HEPA filters housed in portable air cleaners (PACs) located in places with apparently healthy people to prevent possible outbreaks. A method for detecting the presence of SARS-CoV-2 RNA in HEPA filters was developed and validated. The study was conducted for 13 weeks in three indoor environments: school, nursery, and a household of a social health center, all in Ciudad Real, Spain. The environmental monitoring of the presence of SARS-CoV-2 was conducted in HEPA filters and other surfaces of these indoor spaces for a selective screening in asymptomatic population groups. The objective was to limit outbreaks at an early stage. One HEPA filter tested positive in the social health center. After analysis by RT-PCR of SARS-CoV-2 in residents and healthcare workers, one worker tested positive. Therefore, this study provides direct evidence of virus-containing aerosols trapped in HEPA filters and the possibility of using these PACs for environmental monitoring of SARS-CoV-2 while they remove airborne aerosols and trap the virus.