Wastewater Insights for Illinois: Infectious Disease Monitoring for Public Health

The Illinois Department of Public Health (IDPH) leads the Illinois Wastewater Surveillance System (IWSS), supported by the Centers for Disease Control and Prevention (CDC) National Wastewater Surveillance System (NWSS). IDPH shares respiratory viral data generated from wastewater samples collected through the IWSS with CDC, including influenza A viral data, which feeds the CDC influenza A monitoring page. CDC’s Influenza A Wastewater dashboard flags counties that have relatively high influenza A (“flu A”) viral level trends in wastewater compared to levels recorded at that site between October 1, 2023 and March 2, 2024.

To date, there have been no consistently high-level detections (lasting more than one week), suggesting that spikes in flu A in wastewater are transient and do not indicate a significant or sustained outbreak of flu A, thus far. Following identification of elevated levels of influenza A in wastewater, no identification of human or animal cases resulted from follow up in the area. IDPH monitors each event closely and conducts the following actions in response to each high-level flu A detection:

1. Analysis of ER visits in that jurisdiction for influenza-like activity (ILI), to identify any spike in human infections or human outbreaks
2. Analysis of any influenza testing surveillance sites in that jurisdiction, and if any active sites are present, evaluate for unusual or unseasonal activity of flu A (which can serve as a proxy for the H5N1 avian influenza (“bird flu”) outside of the usual flu season)
3. Communication with local health departments to provide the information in order to raise awareness locally as well as receive feedback on any findings from local farms, local healthcare providers or high-risk events in that jurisdiction
4. Communication with the Dept. of Agriculture on these findings
5. Conduct additional analysis on the wastewater findings to determine if bird flu (H5N1) is truly present and contributing to the elevated flu A results

Further, IDPH is prepared to launch additional actions if any persistent presence of high flu A levels in the wastewater are detected beyond the flu season, or if any suspected/documented infections occur in seminal animals such as cattle, or humans.

H5NI avian influenza (“bird flu) refers to the disease caused by infection with avian influenza Type A viruses. These viruses naturally spread among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Bird flu viruses do not normally infect humans. However, sporadic human infections with bird flu viruses have occurred. More information is available on the IDPH website.

Wastewater surveillance involves studying sewage to learn about community health. In May 2021, IDPH enlisted the help of DPI to launch a statewide monitoring program for COVID-19. Wastewater treatment plants from across the state have volunteered to participate in the program, submitting samples twice weekly to monitor COVID-19 trends. Since its launch, the Illinois Wastewater Surveillance System (IWSS) has expanded to include additional respiratory viruses of concern to the public, such as influenza and respiratory syncytial virus (RSV). Samples are processed and analyzed at the University of Illinois Chicago and then sent to Argonne National Laboratory for genetic sequencing and analysis to identify variants. Results are shared with public health decision-makers, wastewater plant operators and the public through a variety of mechanisms (including this dashboard). DPI and Northwestern University are partnering to interpret and present the data in visual ways.