Eastern Equine Encephalitis

Eastern equine encephalitis (EEE or triple E) is a rare but potentially severe illness that can be transmitted by mosquitoes to humans.

Human cases of EEE were reported in the state of Michigan in the summer of 2019, so protect yourself from mosquito bites.

On this page:

  • What is eastern equine encephalitis?
  • What is UHS doing about EEE?
  • Transmission to humans
  • Symptoms
  • Diagnosis
  • Treatment
  • Prevention
  • More information

What is eastern equine encephalitis (EEE)?

EEE is a rare but serious disease caused by the EEE virus (EEEV). It can cause encephalitis, which is inflammation of the brain.

Cases have been identified in Michigan in summer/fall 2019, and cases also occur in other states. You can see the number of confirmed cases in the US on this Map (follow link then scroll down for map).

What is UHS doing about EEE?

UHS is monitoring the situation, in collaboration with Michigan Medicine and the Washtenaw County Health Department, and informing students about risk.


Mosquitoes transmit the virus to people. It is not transmitted from person to person.

People at greatest risk are those who live near woodlands or participate in outdoor recreational activities.


Symptoms develop 4 to 10 days after the bite of an infected mosquito.

Severe cases begin with the sudden onset of headache, high fever, chills, and vomiting. Later disorientation, seizures, and coma may occur. Approximately one third of people who develop EEE die, and many of those who survive have mild to severe brain damage. Children and the elderly are most at risk of severe illness.

If you have symptoms of severe illness, call or visit a health care provider as soon as possible. U-M students and other UHS patients can call for Nurse Advice by Phone, day or night, or see How to Get Health Care.


There is no specific treatment for EEE. Antibiotics are not effective against viruses, and no effective anti-viral drugs have been discovered. Severe illness may be treated by hospitalization, respiratory support, IV fluids, and prevention of other infections.


There is no human vaccine for EEE, but you can reduce the risk of infection by preventing mosquito bites.

  • Avoid situations where you would be exposed to mosquitos. Mosquito-borne illness is a risk in Michigan until late fall when night temperatures consistently fall below freezing. Mosquitos can be active day and night.
  • Apply insect repellent to exposed skin. Products with DEET are effective, and the CDC also recommends other repellents. Follow the manufacturer's directions for use on the label.
  • Spray clothing with repellents because mosquitoes may bite through thin clothing. Follow the manufacturer's directions for use on the label.
  • Cover up: wear long-sleeved shirts and long pants when outdoors.
  • Maintain window and door screens to keep mosquitoes out of buildings.
  • Empty water from mosquito breeding sites.

More information:

University Health Service:

  • How to Get Health Care: Appointments are required for most medical services, however options are available for urgent concerns.
  • Nurse Advice by Phone is available day and night, which may save a trip to UHS, the ER or an urgent care facility.

Washtenaw County Health Department - phone 734-544-6750

Michigan Department of Community Health

Centers for Disease Control and Prevention