A mosquito collected in Wayne County outside Detroit tested positive for West Nile virus, county health officials announced Wednesday, July 22.
The infected insect was trapped somewhere in the Out-Wayne County area, which includes Plymouth and Canton, though officials did not specify the exact collection site. The confirmation means the virus is active in the communities where Plymouth and Canton residents live, work, and spend time outdoors.
Wayne County is now among six Michigan counties with positive mosquito samples this year. Bay, Kent, Midland, Ottawa, and St. Clair counties have also reported detections, with 13 total positive samples statewide, according to state health data.
No human cases have been reported in Michigan so far this summer.
What residents should know
Dr. Avani Sheth, Wayne County Public Health's chief medical health officer, said the detection was not unexpected but urged residents to take precautions.
"We want people to continue enjoying the outdoors this summer," Sheth said Wednesday. "A few simple steps — using insect repellent and emptying standing water around your home — can make a big difference in preventing mosquito bites."
Wayne County Public Health recommends two actions: applying insect repellent containing DEET or picaridin before going outside, and emptying any standing water around the home, including flower pots, bird baths, and clogged gutters where mosquitoes breed.
Who faces the greatest risk
About 20% of people infected with West Nile virus develop symptoms, according to the Detroit News. Those can include fever, headache, body aches, joint pain, vomiting, diarrhea, or rash, appearing two to 14 days after a bite.
People older than 50 or those with weakened immune systems face the most serious danger, including potentially fatal complications such as meningitis or brain infection. No vaccine or specific treatment exists.
National context
The 2026 season started earlier than usual. The CDC reported West Nile activity in 23 states as of early July, the highest number that early in a season in more than a decade, according to a CNN analysis of CDC data. Nationwide, 91 people had tested positive for West Nile virus as of the Wayne County announcement.
Last year, 2,146 people across the U.S. tested positive for West Nile virus, including 49 cases in Michigan, with 172 deaths nationwide, according to CDC year-end data.
West Nile activity in Michigan typically peaks in late August and early September, according to the state Department of Health and Human Services. Residents can track mosquito surveillance results through the Michigan DHHS arbovirus dashboard online.
