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Illinois Wastewater Surveillance System

Wastewater or sewage includes water from households and sewers that can contain human urine and fecal waste. People infected with SARS-CoV-2, the virus that causes COVID-19, can shed the virus in their feces, which means wastewater can be used to detect the virus in the community and estimate the amount of SARS-CoV-2 currently present.

Samples taken from wastewater treatment plants and tested may detect SARS-CoV-2 among the population served by that treatment plant, including asymptomatic cases, individuals who may not seek clinical testing or health care, and those who test at home.

While quantified levels of SARS-CoV-2 in wastewater samples cannot yet be translated to exact case counts, monitoring trends or changes in viral loads over time in a community’s wastewater samples can potentially provide insight into increasing, decreasing, and sustained COVID-19 transmission when considered with other public health metrics.

Trends and SARS-CoV-2 levels should not be compared between treatment plants because of unique variations in treatment plants, including size and contribution from non-human sources like rainwater and industrial fluid.

Wastewater Surveillance in Illinois

The Illinois Department of Public Health contracted with the Discovery Partners Institute (DPI), which is part of the University of Illinois System, in May 2021 to develop the Illinois Wastewater Surveillance System (IWSS) to monitor trends in SARS-CoV-2. IWSS sites and data are represented at

IWSS is funded through the Centers for Disease Control and Prevention (CDC) and participates in and submits wastewater data to the National Wastewater Surveillance System. Illinois and national data are publicly available through the CDC COVID Data Tracker, here:

All 11 COVID-19 Regions in Illinois are represented in the IWSS.

Participating wastewater treatment plant operators collect samples twice weekly and send them to the IWSS testing laboratory at DPI, where samples are prepared and the SARS-CoV-2 levels quantified. RNA samples extracted from wastewater are then sent to Argonne National Laboratory, where they are genetically sequenced to identify variants.

Alongside other data, information collected through wastewater helps IDPH and local health department officials to understand community SARS-CoV-2 transmission and to inform the state’s COVID-19 response.