II. Epidemiology
-
Incidence human cases in U.S.: 6 cases per year (rare)
- However, increased outbreak seen in 2024 on U.S. East Coast
III. Background
- First described in an epidemic Encephalitis affecting horses in 1931, Massachusetts
IV. Pathophysiology
-
Arbovirus (Togavirus) primarily causing Encephalitis in horses (as well as donkeys, zebras)
- Similar Arboviruses include Western Equine Encephalitis and Venezuelan Encephalitis
- Mosquito-bird cycle maintain virus between mammalian infections
- Mammals (horses, humans) do not transmit the virus back to Mosquitos
- Found in eastern north america (esp. coastal plains of the eastern U.S. and gulf coast)
- Most common in Florida, Georgia, Maryland, Wisconsin, and New Jersey
- Seasonal: May to October
- Transmitted to humans via aedes Mosquito Bite (zoonotic infection)
- Incubation 4 to 10 days
V. Findings
- See Encephalitis
- Initial
- Fever
- Headache
- Photophobia
- Myalgias
- Nuchal Rigidity
- Later
- Altered Mental Status to coma
- Seizures
VI. Diagnostics
- See Encephalitis
VII. Management
- See Encephalitis
- Supportive care (including airway protection)
- Additional measures
- Corticosteroids
- Intravenous Immunoglobulin (IVIg) has been used in Western Equine Encephalitis
- Anticonvulsants
VIII. Prognosis
- Mortality >33 to 50%
- High risk fo residual neurologic deficits (including paralysis) and Epilepsy in survivors
IX. Prevention
- See Prevention of Vector-borne Infection
- Eastern Equine Encephalitis Vaccine is only available for horses (not for use in humans)
- Insect Repellent
- Long sleeve shirts and pants
- Avoid outdoors at dusk and evening hours
- Avoid areas of standing water
X. Resources
- Eastern Equine Encephalitis (CDC)
- Eastern Equine Encephalitis (Stat Pearls)
XI. References
- Herbert and Talan (2024) EM: Rap, 9/16/2024