Skip to main content

Eastern Equine Encephalitis Continues to Pose a Threat to Michiganders and Their Animals

For immediate release: October 12, 2021

LANSING, MI - Today, the Michigan Department of Agriculture and Rural Development confirmed the discovery of three new cases of Eastern Equine Encephalitis (EEE) in horses from Genesee and Shiawassee (2) counties. These findings highlight the mosquitoes carrying EEE are still alive and active, and Michiganders still need to take precautions to safeguard their animals and themselves. 

EEE is a dangerous, zoonotic mosquito-borne disease which is typically seen in the state from late summer to early fall. Even though it is now October, the mosquitoes that carry EEE will continue to pose a threat until there has been at least one hard freeze where the temperatures fall below 28 degrees Fahrenheit for several hours. Due to this year's mild fall temperatures, the mosquitoes are continuing to circulate in the environment and spread the virus.

With the addition of these newest cases, Michigan has experienced a total of eight cases of EEE in animals for 2021: one deer from Livingston County and seven horses from Barry, Genesee, Livingston (2), Otsego, and Shiawassee (2) counties. There was also the discovery of one EEE-positive mosquito pool in Barry County.

Fortunately, no human cases of the disease have been identified this year. Overall, while case numbers are down from the total seen in 2020 (41 animal cases and four human cases), there is still a need for Michiganders to actively protect their animals and themselves from EEE.

"When combatting EEE, the date on the calendar is not as important as the temperatures being experienced," said State Veterinarian Nora Wineland, DVM. "Our current mild temperatures mean horse owners should not ease up on taking precautions, including vaccination. Since the mortality rate of EEE in horses can be as high as 90 percent, it is important for owners to work with their veterinarian to ensure their animals are properly vaccinated."

To further protect horses and other domestic animals (such as dogs, sheep, and goats) from the mosquitoes that carry EEE, owners are encouraged to eliminate standing water on their property, place livestock in a barn under fans from dusk to dawn to avoid peak mosquito activity, use insect repellants that are approved for the species, and contact a veterinarian if an animal displays any sign of illness-fever and stumbling, which can progress to being down and struggling to stand.

"Michiganders need to continue taking precautions against mosquitoes as they take advantage of our current mild weather conditions and enjoy outdoor activities," said Dr. Natasha Bagdasarian, chief medical executive at the Michigan Department of Health and Human Services. "People can also be infected with EEE from the bite of a mosquito carrying the virus, which can lead to serious health impacts and even death."

Applying insect repellants, wearing long-sleeved shirts and long pants, maintaining window and door screening, and following other precautions can help Michigan residents avoid mosquito bites and stay healthy.

For more information about EEE, please visit