Eastern Equine Encephalitis

Southern house mosquito
Eastern equine encephalitis virus

Eastern equine encephalitis (EEE) virus is spread to both horses and humans by the bite of an infected Aedes or Culex species mosquito. These mosquitoes typically inhabit swamps and the areas surrounding swamps in rural portions of the country. Although only a few cases of EEE are reported in the United States each year, the condition is very serious. According to the CDC, approximately 30% of people with EEE die, and many survivors face ongoing neurologic issues.

In 2019, Tennessee's first ever human case of EEE was reported in Hamilton County. Although several horses have tested positive for EEE over the past 20 years, the novel presence of a human case in our state is concerning. There are no vaccines to prevent or medicines to treat EEE; you should follow the recommended steps to prevent mosquito bites in order to reduce your chance of infection.

For more information about this disease, see the CDC's Eastern Equine Encephalitis home page.

EEE case map across Tennessee by county

CDC Light Trap

CDC light trap

Mosquito Resting Box

Mosquito resting box

Trinidad Trap

Trinidad trap

For those EEE-infected persons who experience symptoms, the time from infected mosquito bite to feeling sick ranges from 4-10 days. The type of illness that develops depends on the age of the person and other factors, but in general, EEE infection can result in febrile illness or neurologic disease. Febrile illness lasts for 1-2 weeks, and most people recover completely. Signs and symptoms of febrile illness can include:

  • Fever
  • Chills
  • Body aches
  • Joint pain

Neurologic disease resulting from EEE infection can include meningitis (infection of the membranes that surround the brain and spinal cord) or encephalitis (infection of the brain). People who recover from this severe illness are often left with long-term physical or mental impairments, which can range from mild brain dysfunction to severe intellectual or social impairment. In addition to fever and headache, signs and symptoms of neurologic disease can include:

  • Diarrhea
  • Seizures
  • Behavioral changes
  • Drowsiness
  • Coma

For more information, see the CDC's EEE Symptoms, Diagnosis, & Treatment web page.

EEE is diagnosed by a healthcare provider, who can order blood tests to look for evidence of EEE virus infection if you experience the symptoms described above. For more information, see the CDC's EEE Symptoms, Diagnosis, & Treatment web page.