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Sewage Shows Hundreds of Yosemite Tourists Likely had COVID-19

California health officials have determined hundreds of people who visited Yosemite National Park this summer were likely suffering from COVID-19. They arrived at this conclusion after performing an unconventional test — not on the park’s visitors, but on its raw sewage.

“It just struck me as a really good idea,” says Dr. Eric Sergienko of the Mariposa County Health Department. “We really did not have a really good way of monitoring our visitors for COVID-19.” According to tests performed on sewage samples, at least 170 people who visited the park over the 4th of July weekend were infected; the following week, the number dropped down to 60, Sergienko says.

After shutting down for several weeks in March, Yosemite National Park now requires visitors to make reservations to help officials monitor the number of people who pass through the gate. However, because the park is under federal jurisdiction, masks are not required.

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