Mosquito-Borne Illness

Learn more about mosquito-borne illness concerns for McLean County

West Nile Virus

This mosquito-borne disease can cause encephalitis, or an inflammation of the brain. Infected culex mosquitos pass the virus on to birds, other animals and people.

West Nile cases primarily occur in midsummer or early fall. During the 2005 mosquito season, McLean County experienced four cases of West Nile virus, resulting in two deaths.

Learn more about West Nile virus


This mosquito-borne disease was brought to the U.S. by travelers from the Caribbean. It’s now found in more than half of US states, including Illinois. The disease is rarely fatal, but causes symptoms such as severe headache, fever, vomiting, rash and joint paint. Joint pain can linger for several months.

Learn more about Chikungunya

Zika Virus

The Zika Virus is a relatively new mosquito-borne disease. It has become a problem in South America, primarily Brazil. It raised concerns when persons suffering from Zika virus developed Guillain-Barre’ syndrome and affected pregnant women began giving birth to babies with severe birth defects. In response, CDC has issued travel notices for people traveling to regions and certain countries where Zika virus transmission is ongoing.

Learn more about Zika virus