View the most recent UHS ILI surveillance report (PDF)
Influenza-like illness (ILI) is defined as the presence of fever greater than 100 degrees F with cough or sore throat in the absence of a known cause. This is the standard surveillance definition of ILI used by public health epidemiologists to track the incidence of influenza over time. It is intentionally broad to permit a simple measure of counting influenza cases seen in outpatient primary care clinics. However, it will also occasionally count persons with illness caused by other respiratory viruses. Thus it is not highly specific for influenza.
ILI case surveillance is conducted by the Wisconsin Division of Public Health (DPH) and the U.S. Centers for Disease Control and Prevention (CDC). Tracking this activity is how public health officials determine when each year’s flu season begins and when it peaks. ILI data collected by UHS follows the standard format used by these agencies.
UHS is a designated sentinel surveillance site and reports its ILI data weekly to the DPH, CDC and the American College Health Association (ACHA) as part of an established network of similar sites across the state and country.
UHS also does surveillance laboratory testing for respiratory viruses following protocols implemented by WDPH and the Wisconsin State Laboratory of Hygiene (WSLH). Once influenza has been determined to be present in a community most routine testing is discontinued. A small sample of patients continue to be tested weekly to monitor trends in both influenza types and drug-resistance patterns.
Links to Other Surveillance Data
Wisconsin ILI surveillance (DPH)
Wisconsin laboratory surveillance data (WSLH)
U.S. colleges and universities ILI surveillance (ACHA)
Description of surveillance methods and historical data for the U.S
ILI reports are compiled by UHS epidemiologist Craig Roberts, M.S., PA-C.