With diagnostic testing providing a less consistent and less complete picture of COVID-19 infections, residents in eight Central Valley communities now can turn to a different source to watch trends
in the virus’ spread — their wastewater.

Today Healthy Central Valley Together began publicly posting data from testing of samples taken several times a week from each community’s wastewater treatment plant. Easy to read charts show whether the amount of SARS-CoV-2, the virus that causes COVID-19, is rising, falling, or staying the same.

“The method we use is the most sensitive available, and the results it yields have tracked closely with COVID-19 cases in other places,” said Heather Bischel, assistant professor of civil and environmental engineering at University of California, Davis, and project lead for Healthy Central Valley Together. “With more people opting for at-home tests and publicly run asymptomatic diagnostic testing less available, these data paint a more complete, community-level portrait of infection because everyone who uses the bathroom is included in the samples.”

Healthy Central Valley Together is a collaborative project of public health departments, communities, UC Davis and University of California, Merced that works to prevent the spread of COVID-19 by using wastewater to inform public health action in Merced, Stanislaus, and Yolo counties. The participating communities are Davis, Esparto, Los Banos, Merced, Modesto, Turlock, Winters, and Woodland.

The wastewater treatment plants in each community take samples several times a week and send them to a new West Sacramento laboratory for Eurofins Pandemic Prevention Services, a global scientific leader in bioanalytical and environment testing.

“We are increasing health equity by providing a leading approach to wastewater monitoring to parts of the state that thus far have had less access to it,” said Colleen Naughton, assistant professor of civil and environmental engineering at UC Merced and co-principal investigator for Healthy Central Valley Together.

Naughton and colleagues recently found that 70 percent of the wastewater monitoring in California during the pandemic has been done in urban areas in the coastal and southern parts of the state. Because markers of the virus that causes COVID-19 can be found in human waste (also called stool, feces, excrement, or poop) before an infected person shows symptoms — and even if a person never shows symptoms — wastewater monitoring can inform counties and cities about infection trends. This allows them to notify residents and to respond if needed (for example, by encouraging community members to get tested).

Healthy Central Valley Together scientists meet regularly with county public health officials to review the data. Contact: joseph.garcia@gmmb.com