The Chicago Department of Public Health announced that mosquitoes carrying West Nile virus have been identified in Chicago for the first time in 2026.

While infected mosquitoes have now been detected within the city, officials emphasized that no human cases of West Nile virus have been reported in Chicago so far this year.Earlier in May, Illinois health authorities had already found West Nile-positive mosquitoes in other parts of the state.West Nile virus is transmitted to humans through the bites of infected mosquitoes, although most mosquitoes do not carry the virus.Health officials note that the greatest risk of infection occurs between June and October, when mosquito activity is at its peak.According to public health data, most infected individuals experience no symptoms.

However, approximately one in five people may develop fever and flu-like symptoms, including headaches, body aches, vomiting, diarrhea, and skin rashes.

In rare but serious cases, particularly among adults over 55 and people with weakened immune systems, the virus can cause severe neurological illness requiring hospitalization and may even result in death.

Because there are currently no licensed vaccines or specific treatments available for West Nile virus, public health officials stress that prevention is the most effective protection.

Residents are encouraged to use EPA-registered insect repellents, wear long sleeves and pants during peak mosquito hours, maintain window and door screens, remove standing water from containers around their homes, and keep vegetation trimmed.

The city also continues extensive mosquito-control efforts, including treating more than 80,000 storm-water catch basins with larvicides, conducting weekly mosquito surveillance and testing, spraying adult mosquitoes when necessary, and monitoring potential human infections throughout the season.