Eastern

Eastern Equine Encephalitis (EEE)

Eastern Equine Encephalitis (EEE), also known as sleeping sickness, is a rare but serious viral disease that is transmitted to humans and horses by infected mosquitoes. The disease is caused by the Eastern Equine Encephalitis Virus (EEEV), which belongs to the genus Alphavirus within the family Togaviridae. EEE is most commonly found in the eastern and Gulf Coast regions of the United States, as well as parts of Central and South America, and the Caribbean.

Transmission

EEEV is maintained in nature through a cycle involving the Culiseta melanura mosquito and birds living in freshwater hardwood swamps. The virus is transmitted to humans and horses by several species of mosquitoes that become infected after feeding on infected birds. Human and equine cases are considered to be dead-end hosts, as the concentration of virus in their bloodstreams is usually insufficient to infect mosquitoes.

Symptoms

The incubation period for EEE ranges from 4 to 10 days. In humans, EEE can manifest in two forms: systemic or encephalitic (involving swelling of the brain, called encephalitis). The systemic form is characterized by an abrupt onset of chills, fever, malaise, arthralgia, and myalgia. The illness lasts 1 to 2 weeks, and recovery is complete when there is no central nervous system involvement. In the encephalitic form, which occurs in a minority of cases, the patient may experience headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, and paralysis. Approximately a third of patients who develop encephalitis die from the disease.

Diagnosis

Diagnosis of EEE is based on clinical features, geographic location of exposure, and laboratory testing. Laboratory diagnosis is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect virus-specific IgM and neutralizing antibodies. In some cases, the virus can be isolated from blood, CSF, or brain tissue, or it can be detected by PCR (polymerase chain reaction).

Treatment

There is no specific antiviral treatment for EEE. Care is based on symptoms, with supportive therapy including hospitalization, respiratory support, IV fluids, and prevention of secondary infections. Due to the severity of the disease, individuals with suspected EEE should be evaluated by a healthcare provider immediately.

Prevention

Preventive measures focus on community-based mosquito control programs, personal protective measures to avoid mosquito bites, and vaccination of horses. Personal protection includes the use of mosquito repellent, wearing long sleeves and pants, and avoiding outdoor activities during peak mosquito activity times. Vaccines are available for horses but not for humans.

Epidemiology

The incidence of EEE varies annually, but human cases are relatively rare, with only a few cases reported in the United States each year. However, EEE is regarded as one of the most severe mosquito-transmitted diseases in the United States with a high mortality rate among those who develop encephalitis.

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See Also

• West Nile Virus
• Malaria
• Dengue Fever

External Links

• Centers for Disease Control and Prevention (CDC) - Eastern Equine Encephalitis
• World Health Organization (WHO) - Factsheet on Arboviral diseases