WNV Information

West Nile Virus (WNV)

West Nile virus (WNV) is a mosquito-borne disease most commonly spread by the bite of an infected Culex mosquito. WNV first emerged in the eastern U.S. in 1999 and can now be found throughout the 48 contiguous states. In Chicago, human cases are typically seen in summer and fall when mosquitoes are prevalent. While most people infected with WNV do not have symptoms about 1 in 150 develop a serious illness that affects the central nervous system and can result in death. Serious illness can occur in people of any age but those over the age of 60 and those with certain medical conditions are at greater risk.

The incubation period for WNV disease can range from 2 to 14 days.

Mild illness: fever, headache, body aches, joint pains, vomiting, diarrhea, rash

Severe illness: high fever, severe headache, neck stiffness, stupor, disorientation or confusion, coma, tremors, convulsions, muscle weakness, visions loss, numbness, paralysis

Mosquitoes can lay eggs in small amounts of standing water, so limiting their habitats helps reduce the spread of the virus.
  • Regularly empty outdoor water sources such as buckets, flower pots, pool covers, birdbaths and pet dishes.
  • Make sure doors and windows have tight-fitting screens to prevent mosquitos from entering homes.
Reduce personal risk of WNV by taking steps to keep mosquitoes from biting.
  • When possible, stay inside at dusk, dawn and other times of heavy mosquito activity.
  • If you need to be outside, wear long sleeves, long pants and socks and use an EPA- registered insect repellent (see link below) properly to prevent mosquito bites.
  • Find an insect repellent containing the active ingredient DEET, Picaridin, IR3535, Oil of lemon eucalyptus, Para-menthane-diol or 2-undecanone.

No vaccines to prevent
No medications to treat
Nueroinvasive vs Non-neuroinvasive
Grab anything else from here:

Anything for here?
Cross-reactivity with SLE?

WNV Contact Info

For questions please contact the

Communicable Disease Program at


During non-business hours call

311 (or 312-744-5000 if outside the City of Chicago).

Report all cases of WNV to the

Chicago Department of Public Health

by phone (312-743-9000) or

fax (312-746-6388).

WNV Updates

Chicago WNV data brief