Illinois reports first case of West Nile virus in mosquitoes found near Rockford

Rockford — The Illinois Department of Public Health has detected the first mosquitoes of 2025 to test positive for West Nile virus.

The testing pool was collected on Friday in Rockford by the Winnebago County Health Department, and tested positive on Monday, according to an IDPH news release,

“The news of the first batch of mosquitoes carrying West Nile virus is a reminder for Illinois residents to begin protecting themselves from diseases caused by mosquito and tick bites,” IDPH Director Dr. Sameer Vohra said in the announcement.

“The best defense against West Nile virus is to practice the ‘Three R’s’: reduce, repel and report’,” he said.

IDPH urges everyone – especially older adults or those who have weakened immune systems – to ‘Fight the Bite’ and protect themselves and their families from mosquitoes and the viruses they carry,“ Vohra said in the release.

The state reported cases of West Nile were found in 72 counties in 2024. While only 69 human cases were confirmed, mosquitoes, birds, and horses also tested positive for the virus, according to the IDPH.

Of the 69 confirmed human cases, 13 were fatal, the highest number since 2018 when 18 people died of the virus, according to IDPH.

“IDPH maintains a robust surveillance system to monitor West Nile Virus both in the environment, with laboratory testing of mosquito batches and sick horses, and among Illinois residents by investigating and monitoring human infections,” the department said in its announcement.

West Nile is transmitted through mosquitoes that have previously bitten infected birds. Common symptoms of the virus include fever, nausea, headache, and muscle aches. These symptoms may last from a few days to a few weeks.

While most people who contract West Nile virus do not show symptoms, some cases can become severe.

Severe symptoms can include meningitis, encephalitis, or death. People over the age of 60 and individuals with compromised immune systems are at the highest risk of severe illness, according to IDPH.

More information on West Nile Virus, including tracking data for 2025, can be found on the IDPH website.