Surveillance Data

Environmental Health Services conducts surveillance activities for West Nile virus (WNV) seasonally, from May through October, by operating with partner agencies 54 mosquito collection traps currently located throughout DuPage County. These traps are designed to capture the Culex species of mosquitoes, which is the primary transmitter of WNV in our area. After collection, the mosquitoes are tested for the presence of the virus to predict the risk of human exposure.

In addition to the DuPage County Health Department, other public and private agencies conduct mosquito testing in the County, including: City of Naperville, Clarke Environmental Mosquito Management, Inc., Forest Preserve District of DuPage County, and Illinois Department of Public Health. The location and most recent test results can be found on the Surveillance Maps page a few days after the statistics below are updated.

Current Activity Levels 

The table below summarizes the current WNV activity level based on surveillance testing by all agencies this mosquito season.

DuPage County West Nile Virus Surveillance Data 2023Week: 42
10/15 - 10/21
Year to Date
Mosquitoes Tested029,253
WNV Total Tests0914
WNV Positive Tests0176
Positive Mosquito Pool Rate Percent (%)0%19%
Reported Human Cases--16
Communities with Human WNV Cases

Addison, Bartlett, Burr Ridge, Darien, Downers Grove, Glen Ellyn, Hanover Park, Naperville, West Chicago, Wheaton Willowbrook, Woodridge
Personal Protection IndexRisk Level 3


Mosquito Pool Rate and WNV Human Cases 9.5.2023 (PNG)

Bird Reporting

Mosquitoes are infected with WNV after biting infected birds, which are the host or reservoir of the virus in the environment. The presence of dead birds can also be an indicator that the virus is present in an area. Dead bird sightings can be reported by using the reporting tool on the Tick and Dead Bird Report page.

Birds that are reported should be dead no more than 48 hours and have no other obvious causes of death. Within a few hours of your report, you may be contacted by our staff to arrange for pick-up of the bird for further testing. Otherwise, the dead bird can be disposed of by double-bagging and placing in your household trash.

Human Cases

Human cases of WNV are monitored by our Communicable Disease/Epidemiology Team, which receives reports of WNV cases from local doctors, hospitals and laboratories. Human case information will be listed in the surveillance chart above, as cases are reported.

Last Updated: 10/24/2023