County Health Officer Dr. Eric Sergienko says, "There's a lot of chatter now about doing wastewater testing, and for us it made sense. We have a highly mobile population that visits the area, and so it's difficult to capture that data in terms of lab testing and testing people."
The county first started studying its sewage to track the virus back in late May. Samples are now collected once a week from the treatment facilities in Mariposa, Wawona, and El Portal, which gets wastewater from Yosemite Valley.
The tubes are then sent to Boston-based Biobot for analysis. The company initially used its technology to study opioid use, but is now providing COVID-19 testing for about 400 facilities in 42 states across the country.
MORE: Yosemite National Park closes campgrounds again after spike in California COVID-19 cases
Mariposa just received its first positive results Monday from samples that were taken at all three of its sites following the 4th of July weekend.
Dr. Sergienko says, "What that means to me is that we do have people that are coming up into the area that have that virus in their guts, and they are shedding that virus."
Officials say those results are concerning but also indicate the county's current safety precautions are working to prevent widespread outbreaks.
That includes a requirement for all hotels to leave rooms vacant for 24 hours before even cleaning them, which has brought backlash from some in the lodging industry.
Board of Supervisors Chair Kevin Cann says, "We have no reason to deviate from that right now, and you know it's good for the housekeepers, it's good for all the service workers, and it's good for the visitors."
Supervisor Cann says the board is committed to helping businesses that are suffering as a result of COVID-19 restrictions, including a grant program that was just approved Tuesday. But he believes the positive sewage samples reinforce the need for safety first.
"It is a little bit scary to know that that the virus is around, which rededicates us to our processes for sanitization and for working with managing the visitors managing the crowds," says Cann.
The county plans to continue the wastewater testing through January at a price of about $88,000. The county anticipates using federal CARES Act funding to cover the cost.
MORE: Newsom allows some CA salon services to move outdoors