II. Epidemiology

  1. Incidence human cases in U.S.: 6 cases per year (rare)
    1. However, increased outbreak seen in 2024 on U.S. East Coast

III. Background

  1. First described in an epidemic Encephalitis affecting horses in 1931, Massachusetts

IV. Pathophysiology

  1. Arbovirus (Togavirus) primarily causing Encephalitis in horses (as well as donkeys, zebras)
    1. Similar Arboviruses include Western Equine Encephalitis and Venezuelan Encephalitis
    2. Mosquito-bird cycle maintain virus between mammalian infections
    3. Mammals (horses, humans) do not transmit the virus back to Mosquitos
  2. Found in eastern north america (esp. coastal plains of the eastern U.S. and gulf coast)
    1. Most common in Florida, Georgia, Maryland, Wisconsin, and New Jersey
    2. Seasonal: May to October
  3. Transmitted to humans via aedes Mosquito Bite (zoonotic infection)
    1. Incubation 4 to 10 days

V. Findings

  1. See Encephalitis
  2. Initial
    1. Fever
    2. Headache
    3. Photophobia
    4. Myalgias
    5. Nuchal Rigidity
  3. Later
    1. Altered Mental Status to coma
    2. Seizures

VI. Diagnostics

VII. Management

  1. See Encephalitis
  2. Supportive care (including airway protection)
  3. Additional measures
    1. Corticosteroids
    2. Intravenous Immunoglobulin (IVIg) has been used in Western Equine Encephalitis
    3. Anticonvulsants

VIII. Prognosis

  1. Mortality >33 to 50%
  2. High risk fo residual neurologic deficits (including paralysis) and Epilepsy in survivors

IX. Prevention

  1. See Prevention of Vector-borne Infection
  2. Eastern Equine Encephalitis Vaccine is only available for horses (not for use in humans)
  3. Insect Repellent
  4. Long sleeve shirts and pants
  5. Avoid outdoors at dusk and evening hours
  6. Avoid areas of standing water

X. Resources

  1. Eastern Equine Encephalitis (CDC)
    1. https://www.cdc.gov/eastern-equine-encephalitis/site.html
  2. Eastern Equine Encephalitis (Stat Pearls)
    1. https://www.ncbi.nlm.nih.gov/books/NBK557692/

XI. References

  1. Herbert and Talan (2024) EM: Rap, 9/16/2024

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Related Studies

Ontology: Encephalomyelitis, Eastern Equine (C0153065)

Definition (MSH) A form of arboviral encephalitis (primarily affecting equines) endemic to eastern regions of North America. The causative organism (ENCEPHALOMYELITIS VIRUS, EASTERN EQUINE) may be transmitted to humans via the bite of AEDES mosquitoes. Clinical manifestations include the acute onset of fever, HEADACHE, altered mentation, and SEIZURES followed by coma. The condition is fatal in up to 50% of cases. Recovery may be marked by residual neurologic deficits and EPILEPSY. (From Joynt, Clinical Neurology, 1996, Ch26, pp9-10)
Concepts Disease or Syndrome (T047)
MSH D020242
ICD9 062.2
ICD10 A83.2
SnomedCT 40177004, 417496004, 416925005
LNC LA20113-9
English Eastern equine encephalitis, EEE - Eastern equine encephal, EASTERN EQUINE ENCEPH, ENCEPH EASTERN EQUINE, Eastern equine encephalitis (diagnosis), Encephalitis eastern equine, EEE infection, Eastern Equine Encephalitides, Eastern Equine Encephalitis, Encephalitides, Eastern Equine, Encephalitis, Eastern Equine, Equine Encephalitides, Eastern, Equine Encephalitis, Eastern, Eastern Equine Encephalomyelitides, Eastern Equine Encephalomyelitis, Encephalomyelitides, Eastern Equine, Encephalomyelitis, Eastern Equine, Equine Encephalomyelitides, Eastern, Equine Encephalomyelitis, Eastern, East equine encephalitis, Encephalomyelitis, Eastern Equine [Disease/Finding], eee, eastern equine encephalitis, Eastern equine encephalitis (disorder), Eastern Equine Encephalitis (EEE), eastern equine; encephalitis, encephalitis; eastern equine, encephalitis; equine, eastern, equine; encephalitis, eastern, EEE, Eastern equine encephalomyelitis, EEE - Eastern equine encephalitis, Eastern equine encephalitis virus infection, Eastern equine encephalitis virus infection (disorder), Eastern equine encephalitis virus neuroinvasive disease, Neuroinvasive Eastern equine encephalitis virus infection (disorder), Neuroinvasive Eastern equine encephalitis virus infection, Neuroinvasive Eastern equine encephalitis virus disease
Italian Encefalite equina orientale, Encefalite equina tipo est, Infezione da encefalomielite equina orientale, Infezione da virus dell'encefalite equina orientale, Encefalite equina dell'est, Encefalomielite equina dell'est
Dutch eastern equine encephalitis virusinfectie, EEE-infectie, encefalitis; equin, oostelijk, encefalitis; oostelijk equin, equin; encefalitis, oostelijk, oostelijk equin; encefalitis, Oostelijke equine encefalitis, eastern equine encephalitis, Encefalomyelitis, oosterse paarden-, Oosterse paardenencefalomyelitis, Paardenencefalomyelitis, oosterse
French Infection par le virus de l'encéphalite équine de l'Est, Infection à EEE, Encéphalomyélite équine orientale, Encéphalite équine de l'Est, Encéphalite équine nord-américaine de l'Est, Encéphalite équine orientale, Encéphalomyélite équine de l'Est
German Infektion durch den oestlichen Pferdeenzephalitis-Virus, EEE Infektion, Oestliche Pferdeenzephalitis [Eastern-Equine-Encephalitis], oestliche Pferdeenzephalitis, Enzephalomyelitis, östliche Pferde-, Östliche Pferdeenzephalomyelitis
Portuguese Encefalite equinoriental, Infecção por vírus de encefalite equinoriental, Encefalomielite Equina do Leste, Encefalite equino-oriental
Spanish Infección por virus de la EEE, Infección por virus de la encefalitis equina oriental, encefalitis equina oriental (trastorno), encefalomielitis equina oriental, encefalitis equina oriental, Encefalitis equina oriental, infección neuroinvasiva por virus de la encefalitis equina del este (trastorno), infección neuroinvasiva por virus de la encefalitis equina del este, infección neuroinvasiva por virus de la encefalitis equina oriental, infección por virus de la encefalitis equina del este (trastorno), infección por virus de la encefalitis equina del este, infección por virus de la encefalitis equina oriental, Encefalomielitis Equina Oriental, Encefalomielitis Oriental Equina
Japanese 東部ウマ脳炎ウイルス感染, トウブウマノウエンウイルスカンセン, トウブウマノウエン, 東部ウマ脳炎, 脳脊髄炎-東部ウマ, 東部ウマ脳脊髄炎, 東部馬脳炎, 東部馬脳脊髄炎, 脳炎-東部ウマ, 脳炎-東部馬, 脳脊髄炎-東部馬
Swedish Hästencefalomyelit, östlig
Finnish Idän hevosaivotulehdus
Russian LOSHADINYI ENTSEFALOMIELIT VOSTOCHNYI, ENTSEFALOMIELIT LOSHADINYI VOSTOCHNYI, ЛОШАДИНЫЙ ЭНЦЕФАЛОМИЕЛИТ ВОСТОЧНЫЙ, ЭНЦЕФАЛОМИЕЛИТ ЛОШАДИНЫЙ ВОСТОЧНЫЙ
Czech Východní koňská virová encefalitida, Východní koňská encefalitida, východní koňská encefalomyelitida, encefalomyelitida východní koňská, východní koňská encefalitida
Korean 북미동부말 뇌염
Polish Zapalenie mózgu i rdzenia wschodnie koni
Hungarian Keleti ló-encephalitis, Keleti ló-encephalitis vírus fertőzés, EEE fertőzés, keleti ló-encephalitis
Norwegian Heste-encefalomyelitt, østlig, Østlig heste-encefalomyelitt, Østlig heste-encefalitt, Heste-encefalitt, østlig