Michigan reports 1st human case of Eastern equine encephalitis since 2021
Michigan is reporting its first human case of Eastern equine encephalitis, also known as EEE, in five years, with the recent diagnosis of someone who lives in Roscommon County.
That diagnosis might also be the first human case in the U.S. this year.
"EEE is one of the most dangerous mosquito-borne diseases in the U.S., with a 30% fatality rate among people who become ill," said Dr. Natasha Bagdasarian, the state's chief medical executive. An EEE outbreak in Michigan during 2019 resulted in 10 human cases, including six fatalities, along with 46 animal cases.
Eastern equine encephalitis is among the mosquito-borne viruses that can cause illness in both animals and, less frequently, in humans. The Michigan Department of Health and Human Services, which reported the human case on Wednesday, said it had not confirmed any animal-related cases so far this year. There were cases confirmed in domestic horses in Michigan during 2023, 2024 and 2025.
As of mid-August, the Centers for Disease Control had not recorded any human cases for 2026. An average of 11 human cases is reported to the agency each year. "Due to delays in reporting, state, territorial, and local health departments may have more up-to-date information," the CDD added.
Roscommon County is in Northern Lower Michigan.
Michigan officials said state and local health departments are working with the Michigan Department of Agriculture and Rural Development and the Michigan Department of Natural Resources to monitor for signs of EEE in humans, mosquitoes, domestic animals, and wildlife. The stepped-up efforts in Roscommon County include additional mosquito trapping and testing beyond the routine weekly mosquito population checks already scheduled for the season.
Mosquito population checks in Michigan so far this year have found signs of West Nile virus and Jamestown Canyon virus. State officials said they have also found birds and a squirrel that tested positive for West Nile virus this year in Michigan.
Symptoms of EEE
People who become infected with Eastern equine encephalitis might notice fever, headache, chills and nausea, health officials said.
The disease can worsen into inflammation of the brain.
Preventing mosquito-borne illness
Health officials say the best way to prevent mosquito-borne diseases is to avoid mosquito bites.
There are several insect repellents registered with the Environmental Protection Agency that people can apply to themselves before going outside when mosquitoes are active.
People should wear shoes and socks, long pants, and long-sleeved shirts when they are outside in areas where mosquitoes are known to be present.
Because mosquitoes lay their eggs on or near water, people should also inspect their homes and outdoor spaces for potential breeding areas. Clean and flush the water in ornamental fountains, pet bowls and bird baths on a regular basis; and repair or discard containers that stay outside and might normally collect water.
