Eastern Equine Encephalitis
EEE Outbreak Information
With the onset of colder weather throughout the state, the season of risk for arboviral illness has ended in Michigan. However, cases from earlier in the year may continue to be investigated and reported. The Arbovirus Update report below will be updated as needed rather than every week.
So far in 2021, one person, nine horses, one deer, and five birds have tested positive for Eastern Equine Encephalitis (EEE). If EEE is suspected in a horse, it should be reported to the Michigan Department of Agriculture and Rural Development at 800-292-3939 (support may be available to pay for testing). If EEE is suspected in a person, it should be reported to MDHHS at 517-335-8165.In late summer and autumn of 2020, Michigan experienced an outbreak of EEE. EEE is one of the most dangerous mosquito-borne diseases in the United States, with a 33 percent fatality rate in people who become ill. In 2020 there were 4 human cases (including two deaths), and 41 animal cases in Michigan. In an effort to prevent spread of Eastern Equine Encephalitis (EEE), MDHHS conducted aerial mosquito control treatment Sep. 16 - 23, 2020 in certain high-risk areas of Michigan. This treatment was completed successfully and there were no adverse events reported from the aerial treatment.
- EEE 2020
2021 Press Releases
Eastern Equine Encephalitis Continues to Pose a Threat to Michiganders and Their Animals (10/12/2021)
First Mosquitos of 2021 carrying Eastern Equine Encephalitis virus found in Barry County (8/27/2021)
State Confirms Eastern Equine Encephalitis in Livingston County Horse (8/26/2021)
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Arbovirus Update, including Eastern Equine Encephalitis in Michigan (Updated January 20, 2022):
Detailed County Maps
Who is at risk?
Who is at risk of Eastern Equine Encephalitis (EEE) illness?
People who engage in outdoor work and recreational activities in endemic areas are at increased risk of infection. Persons over age 50 and under age 15 seem to be at greatest risk for developing severe disease when infected with EEE. Overall, only about 4-5% of human EEE infections result in EEE illness. EEE infection is thought to confer life-long immunity against re-infection.
Where is EEE a risk in Michigan?
EEE has been reported in animals and people throughout the state. EEE is most commonly found in swamp and bog habitats. All residents of and visitors to areas where EEE activity has been identified are at risk of infection.
No Opt Out
Signs and Symptoms
What are the symptoms of Eastern Equine Encephalitis (EEE) infection?
No symptoms in many people. Most people who become infected with EEE do not develop any symptoms.
Febrile illness in some people. Only 4-5% of people will be become sick when infected with EEE. Some people who are infected will develop chills, fever, weakness, muscle and joint pain. The illness may last up to two weeks. Most people with this type of EEE disease recover completely, but fatigue and weakness can last for weeks or months.
Severe symptoms in a few people. Less than 1% of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues).
- The symptoms of neurologic illness can include high fever, headache, irritability, restlessness, drowsiness, anorexia, vomiting, diarrhea, bluish discoloration of the skin, convulsions, and coma.
- Serious illness can occur in people of any age. However, children and people over 60 years of age are at the greatest risk for severe disease. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk for serious illness.
- Recovery from severe disease may take several weeks or months. Of those who recover, many are left with disabling and progressive mental and physical sequelae, which include can range from minimal brain dysfunction to severe intellectual impairment, personality disorders, seizures, paralysis, and cranial nerve dysfunction. Many patients with severe sequelae die within a few years.
- About 30 percent of people who develop neurologic infection due to Eastern Equine Encephalitis will die.
Diagnosis and Testing
What should I do if I think a family member might have Eastern Equine Encephalitis?
Consult a healthcare provider for evaluation and diagnosis.How is Eastern Equine Encephalitis diagnosed?
Diagnosis is based on a combination of clinical signs and symptoms and specialized laboratory tests of blood or spinal fluid. These tests typically detect antibodies that the immune system makes against the viral infection.Important Links
- Laboratory Testing
- Case Reporting
- Specimen Collection and Submission
Treatment
How is Eastern Equine Encephalitis (EEE) treated?
No human vaccine against EEE infection or specific antiviral treatment for clinical EEEV infections is available. Patients with suspected EEE should be immediately evaluated by a healthcare provider, appropriate serologic and other diagnostic tests ordered, and supportive treatment provided.
Prevention
How do I protect myself and my family from Eastern Equine Encephalitis (EEE)?
There is no vaccine against EEE virus for humans. Reducing exposure to mosquitoes is the best defense against infection with EEE and other mosquito-borne viruses. There are several approaches you and your family can use to prevent and control mosquito-borne diseases.
- Use repellent: When outdoors, use insect repellent containing DEET, picaridin, IR3535 or oil of lemon eucalyptus on exposed skin and/or clothing. The repellent/insecticide permethrin can be used on clothing to protect through several washes. Always follow the directions on the package.
- Wear protective clothing: Wear long sleeves and pants when weather permits.
- Install and repair screens: Have secure, intact screens on windows and doors to keep mosquitoes out.
- Keep mosquitoes from laying eggs near you: Mosquitoes can lay eggs even in small amounts of standing water. Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets, barrels, and tires. Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Empty children's wading pools and store on their side after use.
How do I protect my horse(s) from Eastern Equine Encephalitis (EEE)?Vaccines are available for horses that will protect them from EEE and West Nile virus. Contact your veterinarian for information regarding vaccinations.
Educational Materials
- 2020 EEE Outbreak Response
- FAQ : Eastern Equine Encephalitis and Aerial Treatment
- FAQ : Eastern Equine Encephalitis and Aerial Treatment - Spanish
- FAQ : Eastern Equine Encephalitis and Aerial Treatment - Arabic
- EEE Transmission Cycle (illustration)
- Information for Hunters
- Control Mosquitoes Tip 'n Toss: Mosquito Control Advice
- Spanish - Flyer - Control Mosquitoes Tip 'n Toss: Mosquito Control Advice
- Arabic - Flyer - Control Mosquitoes Tip 'n Toss: Mosquito Control Advice
Data and Statistics
- 2020 Year-End Arbovirus Summary
- 2019 Year-End Arbovirus Summary
- 2020 EEE Outbreak Summary presentation
- Confirmed and probable EEE horse cases, 2020
- Confirmed and probable EEE deer cases, 2020
- Confirmed and probable EEE human cases, 2020
- Mosquitoes tested for Eastern Equine Encephalitis virus in Michigan by County, 2020