CHICAGO — Chicago is harnessing the city’s wastewater streams as a real-time public health monitoring tool, enabling health officials to track community disease trends and guide prevention efforts with data that can arrive days before cases spike in hospitals or clinics.
The Chicago Department of Public Health (CDPH) — in partnership with academic researchers and regional laboratories — has been publishing wastewater surveillance results on its public dashboard, tracking viral levels for SARS-CoV-2, influenza A and B, and Respiratory Syncytial Virus (RSV) based on samples drawn from treatment plants and neighborhood sewersheds across the city.
“We’ve seen wastewater surveillance provide a critical window into disease circulation that isn’t dependent on who shows up at a clinic or gets a test,” said a CDPH official involved in the program, reflecting the department’s view that environmental data is now an essential complement to traditional public health indicators. Wastewater data can help detect rising trends earlier than clinical case counts alone.
Data as an Early Warning System
Chicago’s wastewater monitoring program is part of the broader Respiratory Virus Wastewater Surveillance Dataset, which public health officials update regularly. The dataset shows pathogen concentrations from sites representing major sewer systems, giving a population-level snapshot of respiratory viral activity. (Data.gov)
Beginning in early February 2026, CDPH adjusted how it reports wastewater concentrations, shifting away from population-normalized figures to focus on site-level and overall averages. Officials say this simplifies trend interpretation and better supports timely action.
Health experts emphasize that wastewater signals often precede clinical case data, a feature that has made the approach invaluable during the COVID-19 pandemic and beyond. According to the U.S. Centers for Disease Control and Prevention, wastewater monitoring can show changes in community infection trends before health systems report increased cases, since it captures viral shedding from symptomatic and asymptomatic individuals alike.
Academic and Local Partnerships Fuel the System
The ongoing surveillance work in Chicago builds on a legacy of wastewater epidemiology research that dates back to the early pandemic response and even earlier. Local academic institutions and research collaborations have helped refine sampling methods, genomic sequencing, and neighborhood-level surveillance.
The Discovery Partners Institute (DPI) — with partners including University of Illinois Chicago, Argonne National Laboratory and Northwestern University — has been collecting samples from more than 85 wastewater sites, including Chicago neighborhoods and O’Hare International Airport, to feed data into CDPH reporting.
“We’re analyzing wastewater not just for COVID-19 but influenza and other respiratory viruses, giving public health officials deeper insight into community transmission patterns,” said a public health researcher familiar with DPI’s work, noting that early signals from wastewater often show trends not yet visible in conventional reporting.
Practical Public Health Uses
Chicago’s wastewater data has helped fill gaps created by at-home tests and declining clinical testing rates. Since many people no longer report positive tests to health departments, environmental surveillance offers a collective view of actual pathogen prevalence.
“Wastewater doesn’t lie,” said one epidemiologist involved in interpreting sewage data. “It reflects what’s out there in the community, irrespective of whether someone goes to a clinic or gets tested.” While not precise at the individual level, this population-wide metric informs public health planning, resource allocation, and messaging.
National experts also stress the broader utility of wastewater monitoring. According to CDC guidance, wastewater signals — collected through systems like Chicago’s — can serve as a leading indicator ahead of clinical cases and provide actionable data for health agencies seeking to mitigate outbreaks and allocate resources.
As cities like Chicago continue to refine environmental surveillance methods, public health leaders see wastewater analytics as a permanent pillar of disease monitoring, ready to detect future outbreaks of known pathogens and potentially emerging threats.
“Effective public health surveillance now combines clinical data and environmental signals,” said a CDPH health official. “That dual approach gives communities the best chance to anticipate changes in disease activity and act proactively.”
