LOS ANGELES (CBSLA) – A pilot project utilizing portable high-efficiency particulate absorbing filtration units to detect the presence of the COVID-19 virus in classrooms has already yielded results at two Northern California schools.

In mid-April, Medify Air HEPA filters detected the coronavirus in two classrooms in Davis, about 15 miles west of Sacramento; one at Korematsu Elementary and the other at North Davis Elementary.

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“That’s really scary, but I’m glad they can trace it back,” a parent told CBS Sacramento.

The newly developed surveillance swabbing project is part of a new program by Davis Joint Unified School District and Healthy Davis Together, with UC Davis conducting the testing. The goal is to identify a problem before it can spread.

“It’s basically providing passive testing in place of each child getting tested every single day because it’s monitoring any viral activity in the whole room,” says Dr. Sheri Belafsky.

Belafsky is the medical director for Healthy Davis Together and she oversees medical surveillance for UC Davis Public Health. She says students were tested but no coronavirus was detected.

“From the time the swab was collected and then processed in the lab, and then the results were found and children tested, there is a period of several days and that person’s infection could be waning,” she explains.

HEPA filters are able to effectively capture particles the size of SARS-CoV-2, the virus behind COVID-19. This type of HEPA swabbing has been done in hospitals, but not schools.

Belafsky says all HEPA filters that tested positive were replaced and those have since tested negative. That’s good news for parents who say that with kids, the fight against the spread of the coronavirus is a daily battle.

“They end up being close at lunch with no masks,” a parent says. “It’s hard for kids to keep their mask on.”

Belafsky says district staff will continue to swab classroom filters weekly.

“By having an air filter in place and swabbing, we basically have a sentinel,” Belafsky says.

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The school district encourages parents to sign waivers so their children can immediately be tested if the filters detect the coronavirus again.