San Diego County is now routinely testing wastewater in its own public health lab, providing a new tool to track COVID-19, flu, and RSV, or respiratory syncytial virus, across the community. The move comes after federal funding for a regional COVID-19 wastewater surveillance partnership used to predict outbreaks during the pandemic ended in April 2025.
“Wastewater is a really important surveillance tool. It's kind of new and emerging, and what it does is helps us to provide an early warning system for our community,” said Jeremy Corrigan, director of the San Diego County Public Health Lab.
Wastewater testing captures what’s circulating across the entire community, not just people who get tested or show up at a clinic, Corrigan said.
“There may be people in our community that are not sick enough to go seek health care, so those wouldn't be caught in our clinical testing. Or maybe they don't have access to health care or insurance, and they don't seek health care,” he said.
The lab collects samples from major wastewater treatment plants, including Point Loma, South Bay and Encina. Traces of viruses like COVID-19 or the flu are shed in everyday activities, such as using the bathroom, showering or washing clothes.
“What this wastewater surveillance allows us to do is to get access to all of that data in our community and provide that back to everybody to be able to make informed decisions about their health,” Corrigan said.
The first wastewater sample showed COVID-19 levels remain low, while flu cases are increasing. The trend mirrored the county’s latest clinical data published Thursday, which reported about 1,000 flu cases last week and roughly 140 COVID-19 cases.
For doctors, the data helps guide real-time decisions.
“For me, it’s better to know something than to just kind of try to guess at it. This is another tool in our toolbox that physicians and public health can use to protect the community,” said Dr. William Tseng, assistant chief of staff at Kaiser Permanente.
The county has made the wastewater data public through a new online dashboard.
“We wanted to make it as available as real-time as possible. There's a lot of complex graphs on there, but at the top of the dashboard, you'll see kind of an easy-to-interpret summary,” Corrigan said.
Officials said future wastewater testing could expand to track diseases like hepatitis A, measles, dengue virus, and mpox.
