Illinois has established a network of >75 wastewater treatment plants throughout the state that 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 genetic material (viral RNA) in wastewater. Launched in 2021, IWSS is a collaboration among the Illinois Department of Public Health (IDPH), the University of Illinois, Northwestern University and Argonne National Laboratory. The program delivers actionable information to public health decision makers and Illinois residents alike and contributes to the state’s pandemic preparedness.
Wastewater treatment plants send samples of raw, untreated (“influent”) wastewater from their communities each week to scientists at the University of Illinois Chicago (UIC). The lab at UIC measures how much virus is in the wastewater. Samples are then sent to Argonne National Laboratory for genomic sequencing. Genomic sequencing is the process of reading genetic codes. Different viruses have different genetic codes. By understanding the virus’s genes, we can try to predict how viruses will spread in the community. The data are shared with scientists and public health workers each week and posted to this dashboard for the community.
Because this process depends on regular sample collection, shipping, and laboratory analysis, we make every effort to ensure samples are collected and processed as quickly as possible. However, there may occasionally be data gaps or reporting delays due to wastewater treatment plant operations, sample transportation, or holidays.
Epidemiology is the study of how diseases are spread. Wastewater-based epidemiology (WBE) is a powerful tool that provides a community-wide view of illnesses. People can shed virus in their waste even before they feel sick or seek medical care, so 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, community-wide signal that does not depend on who gets tested, where they seek care, or whether they have symptoms.
Public health experts watch wastewater trends over time and track which viruses are circulating. This information is reviewed alongside clinical data and is especially helpful when 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.
IWSS provides a shared, accessible data stream that supports community awareness and helps everyone stay informed about local health conditions.
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 everyone’s use and understanding and can be used in many ways. For instance, by understanding which viruses are spreading within a community, doctors are better equipped to help their patients, community members can plan their daily lives, and public health workers can evaluate the success of disease reducing efforts.
The Illinois Wastewater Surveillance System submits wastewater data to the CDC’s National Wastewater Surveillance System (NWSS) twice weekly, where it is studied, used for national and regional disease forecasting, and posted to public dashboards found here: https://www.cdc.gov/wastewater/index.html.
No. The data are not intended to be used for either type of comparison.
Wastewater measurements for different diseases cannot be directly compared because each virus is measured using a different laboratory test and behaves differently in wastewater. Likewise, measurements for the same disease should not be used to compare one community to another, as wastewater systems, population size, sewer infrastructure, and other local factors can influence the amount of virus detected.
Instead, the data are best used to track trends over time at an individual site. Look for whether levels of a specific disease are increasing, decreasing, or remaining stable within the same community.
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.
Wastewater and clinical data tell different sides of the same story. They measure disease in different ways, so they often – but do not always – match. Clinical data only includes people who get tested or receive medical care, while wastewater data represents all infected people in the community who use the sewer system, even if they do not get tested or have symptoms.
Additionally, people can continue to shed virus into wastewater for days or weeks after they would no longer test positive. Because of this, wastewater levels may stay high even when reported cases are going down.
Furthermore, different versions of a virus, such as COVID-19 variants or flu strains, can also affect how much virus people shed and how long they shed it. These are some of the main reasons why wastewater trends can look different from clinical reports.
Yes! We are working now to expand disease targets to provide more community health information to Illinoisans.
Participation in the program is voluntary. There is no cost to the plant or local taxpayers to participate and the IWSS is currently accepting new plant participants. Please contact us if your wastewater treatment facility would like to participate!
You can use the map on the main page to locate either your plant, or the plant closest to your home. You can also go to the “Locations” tab and search for a city or county. Not all counties in Illinois have a plant participating in IWSS.
80% of Illinois is sewered and we cover 75%, and nearly everyone interacts with sewered systems in some ways, whether at schools, gas stations, etc.
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 sample represents an entire community and does not reflect any one household, business, or individual.
The IWSS is wholly funded by the US Centers for Disease Control’s Epidemiology and Laboratory Capacity grant. ELC supports all 50 state health departments and forms the foundation of our national public health system. Wastewater surveillance in Illinois costs less than twenty five cents per Illinoisan per year.
Please reach out to iwss-admin@uillinois.edu with any questions you may have.
Not all homes and communities in Illinois are sewered, so homes and businesses on individual septic systems are not directly represented by IWSS data. However, communities with homes served by septic systems can still use wastewater surveillance data because these data represent neighboring communities that are likely reflective of the region. Additionally, most people regularly interact with sewer systems in one way or another throughout their daily lives, whether it’s at work, the local gas station, school, or grocery store.
If a substantial portion of your community uses septic systems, the wastewater data may not reflect disease activity for the entire community. However, the data can still provide valuable information about trends among the population served by the sewer system and can complement other public health information, such as clinical testing, emergency department visits, or school absenteeism.