The California Department of Public Health (CDPH) and the California State Water Resources Control Board (SWRCB) together are coordinating with several wastewater utilities, local health departments, universities, and laboratories in California on wastewater surveillance for SARS-CoV-2, the virus causing COVID-19. Data collected from this network of participants, called the California Surveillance of Wastewater Systems (Cal-SuWers) Network, are submitted to the U.S. Centers for Disease Control and Prevention (CDC) National Wastewater Surveillance System (NWSS).

During the COVID-19 pandemic, it has been used for the detection and quantification of SARS-CoV-2 virus shed into wastewater via feces of infected persons. Wastewater surveillance tracks ""pooled samples"" that reflect the overall disease activity for a community serviced by the wastewater treatment plant (an area known as a ""sewershed""), rather than tracking samples from individual people. Notably, while SARS-CoV-2 virus is shed fecally by infected persons, COVID-19 is spread primarily through the respiratory route, and there is no evidence to date that exposure to treated or untreated wastewater has led to infection with COVID-19.

Collecting and analyzing wastewater samples for the overall amount of SARS-CoV-2 viral particles present can help inform public health about the level of viral transmission within a community. Data from wastewater testing are not intended to replace existing COVID-19 surveillance systems, but are meant to complement them. While wastewater surveillance cannot determine the exact number of infected persons in the area being monitored, it can provide the overall trend of virus concentration within that community. With our local partners, the SWRCB and CDPH are currently monitoring and quantifying levels of SARS-CoV-2 at the headworks or ""influent"" of 21 wastewater treatment plants representing approximately 48% of California's population."