Positive test results in Williamson and Washington counties add to a total of 18 upstate counties affected. It's an addition of five more counties just in the past week.
A county is considered positive for West Nile virus if even one bird, mosquito, horse or human from that county tests positive for the virus. So far this year, Illinois officials report 10 positive birds and 33 positive mosquito batches. No other animal or human cases have been reported this year.
A total of 119 cases were reported in 2023, along with six West Nile-related deaths statewide.
West Nile virus is the leading cause of mosquito-borne disease in the continental United States. It is most commonly spread to people by the bite of an infected mosquito.
There are no vaccines to prevent or medicines to treat West Nile in people. About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness.
On the Net:
IDPH West Nile virus page
