Air samplers placed in school cafeterias provided an accurate look at a flu epidemic and at constant low levels of COVID-19 infections in a K-12 school district during the 2022-23 school year, according to a new study from researchers at the University of Wisconsin School of Medicine and Public Health.

“As widespread community testing for the coronavirus wanes, it appears that air sampling can provide a good awareness of the presence of both the influenza A virus and the SARS-CoV-2 virus that causes COVID-19,” said Dr. Jonathan Temte, lead author of the study, and professor of family medicine and community health, UW School of Medicine and Public Health, where he is also associate dean for public health and community engagement. “Schools are excellent places to test these methods because of their role in spreading respiratory viruses.”

The study, which was published in JAMA Network Open, took place in the Oregon School District, a suburban district with about 4,100 students located about 10 miles south of Madison. It is part of a long-running respiratory virus surveillance project called Oregon Child Absenteeism due to Respiratory Disease Study, or ORCHARDS, that began in 2013. Results from air monitors placed in seven school buildings, which trapped virus particles in their filters, were compared with three other surveillance methods: school-based testing of student using rapid antigen testing, a daily count of student absenteeism due to suspected respiratory viruses, and home-based specimen collection by students with testing using reverse transcription-polymerase chain reaction tests at the Wisconsin State Laboratory of Hygiene.

All four methods showed similar respiratory disease patterns during the 22-week study period. They portrayed an influenza A outbreak that peaked from Dec. 11 to Dec. 24, 2022, and dropped precipitously following winter break. By contrast, the SARS-CoV-2 virus was detected at low to moderate levels in at least two school buildings per week from the beginning of the school year through the end of Jan. 2023. There was one difference between methods: school-based rapid antigen testing did not pick up any COVID-19 virus following winter break although the other methods did.

“All the methods demonstrated the ‘epidemic’ nature of influenza and the constancy of SARS-CoV-2 over the assessment period,” Temte said.

Air sampling was shown to be effective in detecting virus particles, but has other advantages, because this method is a non-invasive and anonymous way to keep track of disease outbreaks, he added.


Funding was provided by the Centers for Disease Control and Prevention through cooperative agreement No. 6 U01CK000630-01-01 and financial support to Drs. David and Shelby O’Connor through the Rockefeller Regional Accelerator for Genomic Surveillance.