The risk of West Nile virus in Chicago is considered “high,” as health officials say the area is experiencing “a higher proportion of mosquitoes testing positive for West Nile virus than usual.”

Local health officials say Chicago has reached a “high risk” level of the West Nile virus because mosquitoes are testing positive earlier and could lead to a longer lasting, heightened risk this

The patients range from 40 to 80 years old and reside on the Northwest and South sides. The patients’ symptoms began in late July or early August, according to the Chicago Department of Public Health.