SPRINGFIELD, Ill. (AP) – State officials have confirmed the first human case of West Nile virus in Illinois this year.

The Illinois Department of Public Health said Monday that an adolescent in west-central Illinois became ill with the virus late last month. Health department officials say the first human case came much earlier this year. Human cases of the mosquito-borne virus usually aren’t reported until the end of July or beginning of August. Last year’s first human case was reported Aug. 19, 2015.

There were 77 human cases last year including nine deaths.

Health department officials say the early onset this year means it’s important for Illinoisans to protect themselves against the virus. The virus is spread through mosquito bites. Symptoms include fever, nausea, headache and muscle aches.