Illinois has established a network of >75 wastewater treatment plants throughout the state to submit weekly wastewater samples that are used to track several diseases of public health importance. Specifically, the levels of influenza A, influenza B, Respiratory Syncytial Virus (RSV) and SARS-CoV-2 (COVID) are tracked by measuring the amount of viral RNA in wastewater. The initiative is a collaboration between the Illinois Department of Public Health (IDPH) and the University of Illinois System’s Discovery Partners Institute (DPI). Additional partners include the University of Illinois Chicago, Northwestern University and Argonne National Laboratory. The program aims to deliver actionable information to public health decision makers and Illinois residents alike and contributes to the state’s pandemic preparedness.
Wastewater-based epidemiology (WBE) offers a powerful, community-wide view of respiratory illnesses like influenza A and B, RSV, and COVID-19. People can shed virus in their waste even before they feel sick or seek medical care, which means wastewater can show signs of illness earlier than traditional clinical data. Because everyone in a sewershed contributes to the system, wastewater monitoring provides an anonymous, population-level signal that does not depend on who gets tested, where they seek care, or whether they have symptoms.
Public health experts analyze wastewater trends over time and, in some cases, sequence samples to detect which virus strains are circulating. This information complements clinical data and helps fill gaps—especially when at-home testing is common or diagnostic testing is limited. Wastewater data can alert communities to increases in illness before they appear in clinics or hospitals, giving leaders, health departments, and residents an early opportunity to take protective actions.
WBE is a shared, accessible data stream that supports community awareness and helps everyone stay informed about local health conditions.
Wastewater sampling occurs at the treatment plant level and consists of plant operators collecting a very small amount of water throughout the day as millions of gallons of wastewater flow into the plant. This 24-hour composite sample is representative of an entire community and is not reflective of any one household, business, or individual.
The program is currently prioritizing wastewater treatment plants serving the largest population center in each Illinois county. Participation in the program is voluntary and some counties do not have wastewater treatment plants. There is no cost to the plant or local taxpayers to participate.
A non-detect means either that the virus is not present in the wastewater or that the amount of viral RNA is too little to be reliably detected by the laboratory. A non-detect does not necessarily mean that there are no infected individuals within the associated community.
No. Wastewater data alone will not drive public health interventions such as masking orders or shutdowns. Rather, we hope this is a tool for communities to use along with other resources to help protect their citizens.
The Illinois Wastewater Surveillance System provides information on the levels of viral diseases found in a community’s wastewater. This data is presented publicly for each of us to use as we see fit in our daily lives. Wastewater trends are useful to provide information at the community level.
The Illinois Wastewater Surveillance System submits wastewater data that are published to the Centers for Disease Control and Prevention (CDC) COVID Data Tracker, where it is presented as a 15-day percent change among other metrics: CDC COVID Data Tracker.
The program occasionally experiences logistical difficulties in sample collection related to local conditions at the plant, issues with transit logistics, or observed holidays. Every effort is made to support the timely collection and shipping of samples for analysis.
While the virus that causes COVID-19 has been found in untreated wastewater, there is no evidence that anyone has contracted COVID-19 by this exposure and the risk of transmission from properly designed and maintained sewerage systems is thought to be low. For sample collectors, both CDC and the Environmental Protection Agency (EPA) recommend standard protective equipment and procedures associated with working with wastewater.
Yes! We are working now to expand disease targets to provide more community health information to Illinoisans.
Because each pathogen is distinct, it is not appropriate to compare their viral gene copy numbers, even at the same site. Instead, increasing or decreasing trends in SARS-CoV-2, influenza, or RSV concentrations can be used to understand if cases or hospitalizations for each pathogen are likely to increase or decrease in the community.
You can use the map on the main page to locate either your sewershed, or the sewershed closest to your home. You can also go to the “Locations” tab and search for city or county.
If you live in Cook County, most of the population is served by an organization called the Metropolitan Water Reclamation District of Greater Chicago (MWRD). You can zoom in on the coverage areas for each MWRD plant to understand which plant serves your community. For example, if you live in Blue Island, you can click through the MWRD plants and zoom in to see what areas each covers. If you click on Calumet Water Reclamation Plant (WRP) you will see Blue Island in the shaded coverage area. This means that wastewater flowing from your house in Blue Island goes to the Calumet WRP for treatment. The data points you see on the dashboard for Calumet WRP are from samples taken from raw influent collected as wastewater enters the facility.
Please reach out to iwss-admin@uillinois.edu with any questions you may have.
