Surveillance Data

0Environmental Health Services conducts surveillance activities for West Nile virus (WNV) seasonally, from May through October, by operating 30 mosquito collection traps 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 Health Department, several other public and private agencies conduct mosquito testing in the County. The location and most recent test results can be found on the Surveillance Maps page.

Current Activity Levels

The chart below summarizes the current WNV activity level based on surveillance testing by all agencies.

DuPage County West Nile Virus Surveillance Data 2019Week: 43
Year to Date
Mosquitoes Tested22435,317
WNV Total Tests91,011
WNV Positive Tests087
Positive Mosquito Pool Rate Percent (%)0%9%
Reported Human Cases06
Communities with Human WNV Cases0Bensenville, Glen Ellyn, Lisle, Lombard, Naperville
Personal Protection IndexRisk Level 0


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. After reporting, 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 Unit, 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.