The Illinois Department of Public Health confirms the first human case of West Nile virus in the state for 2016.

In a press release, officials confirm an adolescent in west central Illinois became severely ill from the virus in late May.

Officials say this is unusually early for the first human West Nile case to surface. In most years, human cases don’t pop up until late July or early August.

West Nile virus is transmitted by mosquitoes who have fed on infected birds. Most people infected with West Nile show no symptoms. For others, the virus could result in anything from fever and muscle aches to meningitis and even death.