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Michigan health officials find potentially deadly EEE virus in mosquitoes

Michigan health officials found mosquitoes in Bay County that were infected by Eastern equine encephalitis virus, potentially lethal if transmitted to humans. (Shutterstock)
  • A sample of mosquitoes in Bay County tested positive for Eastern equine encephalitis virus
  • The virus is one of the most dangerous mosquito-borne illnesses, and can be lethal if contracted by humans and animals  
  • Michigan residents are reminded to used bug spray and other preventative measures when outside 

Michigan health officials have issued a warning about mosquitos in Bay County that tested positive for Eastern equine encephalitis virus, a potentially deadly virus that can be transmitted to humans and animals. 

The virus is spread through the bite of infected mosquitoes. Most people who are infected don’t usually have any symptoms according to the  U.S. Center for Disease Control and Prevention.  Symptoms include fever, chills, body aches and joint pain and can show up in the first four to 10 days and can last up to two weeks.


Severe cases can cause infection of the brain (encephalitis) or the membranes around the brain and spinal cord (meningitis). People who develop symptoms such as fever, headache, vomiting, diarrhea, seizures, behavioral changes, drowsiness may be showing signs of a neurological disease.


Though human cases of Eastern equine encephalitis virus are rare, nearly 30 percent of people who are infected by it die, according to the CDC. It is even more deadly among horses. There is a 90 percent fatality rate for infected horses. There have been 189 human cases of the virus and 78 deaths in the U.S. between 2003 and 2022, according to CDC data

Cases involving humans and animals have been reported in Michigan, Wisconsin and Montana but it is most common in states off the Gulf of Mexico.  The virus sickened one Michigan resident in 2021, four in 2020  and 10 in 2019, the department confirmed. Six Michigan residents died from the virus in 2019 and two more in 2020. 

"This detection shows the virus is present in the environment and highlights the need to take precautions,”  Nora Wineland, state veterinarian and director of the Michigan Department of Agriculture and Rural Development’s Animal Industry Division, said in a statement.

Health officials warn residents spending time outside to use insect repellent, wear light colored clothes or long sleeve shirts and remove containers that hold water such as  old tires and buckets to prevent mosquitoes from laying eggs.


For the past three years, the state has offered virus testing for mosquito pools collected by local health departments and county mosquito control programs. 

The increase in mosquitoes infected by the virus likely reflects increased awareness and testing but may also be due to an increase in the presence of the virus in the environment,” the MDHHS said in a press release. 

Last month, the department also reported that a pool of mosquitos in Saginaw County tested positive for Jamestown Canyon virus, a mosquito borne-illness common in the Midwest.

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