Mosquito-borne encephalitis cases emerge in Michigan

Mark Hicks
The Detroit News

The Michigan Department of Health and Human Services confirmed a case of a mosquito-borne disease in a resident and suspect three others, officials announced Monday.

Eastern equine encephalitis is one of the most dangerous mosquito-borne diseases in the U.S. It can be fatal and often leaves survivors with brain damage.

The confirmed case of California encephalitis virus was in Genesee County, while the three cases of Eastern equine encephalitis are suspected in residents from Kalamazoo and Berrien counties, the department said in a statement.

Through Monday, six cases of Eastern equine encephalitis had been confirmed in horses that died in Barry, Kalamazoo and St. Joseph counties, while two had been diagnosed in deer in Barry and Cass counties, state officials reported.

Eastern equine encephalitis, or EEE, is among the most dangerous mosquito-borne diseases in the United States. It has a 33% fatality rate in people who become ill and a 90% fatality rate in horses, according to the release.

Signs of EEE include the sudden onset of fever, chills, and body and joint aches. Symptoms of California encephalitis virus include fever, headache, nausea, vomiting, fatigue and lethargy, state officials said.

Both diseases can develop into severe encephalitis, resulting in headache, disorientation, tremors, seizures and paralysis. Permanent brain damage, coma and death may occur. 

“Mosquito-borne diseases can cause long-term health effects in people and even death,” said Dr. Mary Grace Stobierski,  Michigan Department of Health and Human Services state public health veterinarian and manager of the Zoonotic and Emerging Infectious Diseases Section.

“These cases, along with confirmed cases in horses and deer in the state, stress the importance of taking precautions against mosquito bites.”

To protect against disease-spreading mosquitoes, health officials advise residents to:

• Apply insect repellents with the active ingredient DEET, or other U.S. Environmental Protection Agency-approved product ,to exposed skin or clothing

• Wear long-sleeved shirts and long pants when outdoors

• Maintain window and door screening to help keep mosquitoes outside

• Empty water from mosquito breeding sites around the home, such as buckets, unused kiddie pools, old tires or similar sites where mosquitoes may lay eggs

• Use nets and/or fans over outdoor eating areas

Southwest Michigan has experienced outbreaks of the disease in people and horses in the past, with the most recent outbreaks occurring in the early 1980s, mid-1990s and 2010. 

Three people were infected in Michigan in 2016.

For information about mosquito-borne diseases, go to

The Associated Press contributed to this report.