The Washington Wastewater-Based Epidemiology (WAWBE) program coordinates wastewater testing to monitor infectious disease pathogens in Washington state. WAWBE was established in 2020 in collaboration with the Centers for Disease Control and Prevention National Wastewater Surveillance System (CDC NWSS). The program is located within DOH’s Office of Communicable Disease Epidemiology.
WAWBE collaborates with:
- DOH subject matter experts
- Wastewater utilities
- Local Health Jurisdictions (LHJs)
- Washington State Public Health Lab (PHL)
- Universities and colleges
How Wastewater Monitoring Works
When people are sick, they release germs, or pathogens, in their urine, stool, and other bodily fluids. These germs enter the sewage system when people flush toilets, take showers, or even brush their teeth. By measuring the amount of germs in this sewage (wastewater), we learn which infectious diseases are in our communities and make informed decisions about how to stop sickness from spreading. We call this process “wastewater-based epidemiology.”
After wastewater flows through a network of pipes, it reaches a community wastewater treatment plant. A laboratory tests samples of the wastewater to determine if a pathogen's genetic material is present (called pathogen detection) and, if possible, how much there is (called pathogen concentration). In the WAWBE program, we process the laboratory results to share actionable data with health partners and the public.
Wastewater testing helps us understand the burden of disease in Washington communities. Public health partners use wastewater data with other surveillance measures (like case counts and hospitalization rates) to allocate resources, communicate about concerning transmission trends, and take other public health actions. Community members can use wastewater data to make personal health decisions, such as wearing a mask or staying up-to-date on vaccinations.
Wastewater Testing in Washington
As of September 2025, more than half of Washington’s population is served by a wastewater utility that contributes to WAWBE monitoring. WAWBE and local health jurisdictions (LHJs) work together to select and onboard utilities for our sampling and testing services.
All facilities that participate in the WAWBE program test for a list of routine pathogens, including:
- SARS-CoV-2 (COVID-19), including sequencing to identify circulating variants
- Influenza A & B (flu), including H5 subtyping related to highly pathogenic avian influenza (HPAI)
- Respiratory Syncytial Virus (RSV) A & B
- Mpox, including Clade I testing
Additional pathogens may be tested at specific wastewater utilities representing populations that have a higher risk for infections.
Initially, WAWBE only tested wastewater for SARS-CoV-2, the pathogen that causes COVID-19. Research showed the expanding use of wastewater testing beyond SARS-CoV-2, so we began monitoring more pathogens. We work with pathogen subject matter experts at DOH and LHJs to determine which pathogens to test.
WAWBE sometimes collaborates with academic institutions to assess the feasibility of testing new pathogens at some wastewater utilities. This helps us ensure the results from new pathogens are reliable and actionable before we incorporate them into our routine testing.
Reporting Our Results
WAWBE pathogen subject matter experts decide how to publicly display our data. Wastewater results are also shared with external partners, including wastewater treatment plants, LHJs, and the CDC. These partners may display our data on their own public dashboards, such as the CDC’s National Wastewater Surveillance System.
WA DOH Respiratory Illness Data Dashboard
CDC National Wastewater Surveillance System (NWSS) dashboards
Benefits of Wastewater-Based Epidemiology
Anonymity: Wastewater samples are community samples, meaning individuals cannot be identified through routine pathogen testing.
Passive System: People in the community contribute to the wastewater sample without needing to visit a doctor or health care facility.
Resource Efficiency: Each wastewater sample can be tested for many pathogens at once. A community can monitor multiple public health concerns using the same wastewater sample.
Early Warning: Wastewater data can sometimes show a pathogen is spreading before other public health data sources, such as case counts or hospitalization rates. The timing of this depends on the pathogen and the availability of other data sources.
Limitations of Wastewater-Based Epidemiology
Identifying Cases: Wastewater testing cannot be used to diagnose individual cases of a disease or directly estimate the number of cases within the community.
Non-Detections: The absence of a pathogen in a wastewater sample does not necessarily mean there are no cases within the community. For instance, after a heavy rainfall, storm drain runoff can dilute the wastewater, making pathogen detection more difficult.
Complementary Data Source: It is difficult to fully understand disease burden in a community from wastewater alone. Wastewater data is most impactful when it’s interpreted with other public health data sources, such as case counts or hospitalization rates.
Environmental Sample: Wastewater is not just made up of what comes from homes. It also often includes waste from businesses, factories, and farms. Sometimes, chemicals from homes and other non-household sources are discharged into wastewater that can break down pathogen material as it travels through the pipes. This degradation of the viral or bacterial material within a sample can make the pathogen more difficult to detect once it reaches the lab.
Resources
CDC National Wastewater Surveillance System (NWSS)
Water Environment Federation (WEF) Network of Wastewater-Based Epidemiology (NWBE)
NACCHO Wastewater Surveillance Resource Library
Contact Us
Email WAWBE program for more information.
Washington residents or health care providers should contact their local health jurisdictions for assistance.