Agencies use sewer water to trace COVID-19 spread
Cal researchers help county to look for signs of outbreaks
What goes in must come out, and if it’s the coronavirus coming out, Marin County health officials are aiming to find it in the sewer.
Through a partnership withMarin’s sewage collection agencies and a team of researchers at the University of California, Berkeley, the county has launched a new wastewater surveillance program that detects the presence of the coronavirus in fecal particles.
The program is intended to provide early warning signs for COVID-19 outbreaks in the county, said Dr. MattWillis, Marin’s public health officer.
“When someone is infected with COVID-19, in addition to the usual respiratory symptoms, the virus also travels into our gastrointestinal tract and some amount ends up passing into the toilet,” Willis said.
As a result, he said, “We can test water supplies to see how much virus is present in whole communities based on virus levels in sewage.”
Six sewage agencies in Marin are participating in the program. Collectively, they are sampling wastewater from11 locations, including Marin City, Sausalito, Mill Valley, the Tiburon Peninsula, the Ross Valley, Novato and San Rafael.
The samples are collected by staff at each sewage agency twice per week and are shipped in test tubes to a research lab at the Berkeley Water Center, which is spearheading the program. Scientists analyze the samples to determine the number of coronavirus particles they contain, and then provide the data to public health officials.
Although the data don’t tell health officialswho is infected, they can provide an overview of how widespread the virus is within a community, said Sasha Harris-Lovett, a post-doctoral fellow at the center.
“It’s not biased by who gets tested or who has access to medical care, it’s really everybody who uses the toilet,” Lovett said. “So these data can provide an early warning for surges or trends.”
The programis funded in part by a private grant from an anonymous donor, according to Lovett. In addition to Marin, Contra Costa, San Francisco and Alameda counties are also participating in the program.
Sewage agencies regularly sample the wastewater that flows into their treatment plants using automated-machines. The machines collect small amounts of water about every 15 minutes for 24 hours to make up a single sample.
Central Marin Sanitation Agency is collecting samples from five locations for the program, including one that funnels wastewater from San Rafael’s Canal neighborhood, which has been the site of an ongoing coronavirus outbreak.
“We’re glad to participate and be helpful in using these predictive tools,” said Jason Dow, the agency’s general manager.
The programis also sampling water that flows out of San Quentin State Prison, where more than two thirds of the inmates were infected with COVID-19 in an outbreak over the summer.
“By monitoring this on a regular basis, we increase our chances of detecting if and when there’s another outbreak, potentially before any new cases are diagnosed,” Willis said.
If coronavirus particles are found in San Quentin’s wastewater, crews can install sampling machines at each building within the prison complex to determine amore precise location where people are infected, Willis said. The inmates and staff in the buildings where the virus has been detected could then be tested for COVID-19.
“Early detection is a key to limiting spread,” Willis said.
The programis inits early stages, and health officials are still working to determine how the data can best beused, according to Willis.
“Once the process is validated and proven, we’ll be sharing the results publicly,” he said.
Harris-Lovett said the wastewater data aren’t intended to replace traditional testing methods for detecting COVID-19 cases.
“It’s really designed to be complementary to other kinds of data the public health professionals are using to base their decisions on, like where to provide a pop-up testing site, or to tell hospitals we’re expecting a surge in cases,” she said.