Eastern equine encephalitis (EEE) is a rare disease that is spread to horses and humans by infected mosquitoes. It is among the most serious of a group of mosquito-borne virus diseases that can affect the central nervous system and cause severe complications and even death.
Similar diseases are western equine encephalitis, St. Louis encephalitis, and LaCrosse encephalitis.
The virus can be found in the eastern, Gulf, and north-central areas of the U.S. Most activity occurs between May and August but it can be seen throughout the year in Florida.
Disease Prevention
Learn about steps that can be taken to help prevent mosquito and tick bites and ways to maximize protection against vector-borne illnesses.
Transmission
These mosquitoes can transmit the virus to animals and people. After infection, the virus invades the central nervous system, including the spinal cord and brain. In addition to horses, other animals such as ratites (emus and ostriches) and camelids (alpacas and llamas) can also be impacted by EEE.
- Eastern equine encephalitis is caused by a virus usually spread to people through the bite of an infected mosquito.
- Eastern equine encephalitis virus circulates in the environment between mosquitoes and birds typically found in swamps.
- The virus can rarely be transmitted through solid organ transplantation.
Symptoms
Most people infected with eastern equine encephalitis virus do not develop symptoms. For those who develop symptoms, the time from an infected mosquito bite to onset of illness (incubation period) ranges from 4 to 10 days.
Eastern equine encephalitis virus infection can result in febrile illness (fever) or neurologic disease. The type of illness will depend on the age of the person and other factors.
Testing
Diagnosis is based on tests of blood or spinal fluid.
Treatment
There is currently no therapeutic treatment for EEE. Current methods consist primarily of symptom treatment and supportive care.
- A vaccine has been developed and is in use for horses, as the case-fatality in equines is 80-90%
- There is currently no vaccine for humans.
Resources
- Data and Maps for Eastern Equine Encephalitis
- Detection of eastern equine encephalomyelitis virus RNA in North American snakes
- Florida Department of Agriculture and Consumer Services – Suspected or known cases of EEE must be reported to the State Veterinarian Office
Information for Health Care Providers
Disease Reporting Requirement
All practitioners, health care facilities, and laboratories in Florida are required to notify the Florida Department of Health of diseases or conditions of public health significance under section 381.0031, Florida Statutes, and Chapter 64D-3, Florida Administrative Code.