Eastern equine encephalitis is an arthropod-borne encephalitis associated with eastern equine encephalitis virus and mosquito-borne transmission. [1][3]
Disease overview
Eastern equine encephalitis
东部马脑炎
Evidence-backed informationEN 6/7 applicable sections · ZH 6/7 applicable sectionsUpdated Sep 3, 2026
Eastern equine encephalitis is a rare mosquito-borne viral disease that can cause encephalomyelitis. In the United States, fewer than 10 human cases are reported in a typical year, although many infections are estimated to be asymptomatic. [1][2]
Read the full clinical and epidemiological profile7
Most infections are asymptomatic. When the central nervous system is involved, eastern equine encephalitis can cause encephalitis or encephalomyelitis. [1][2]
In the United States, eastern equine encephalitis occurs mainly in Atlantic and Gulf Coast states and in some areas near the Great Lakes. Human cases are rare, with most occurring from summer through early fall when mosquito activity is greatest; Florida reports human and equid cases throughout the year. [1]
Transmission is maintained in an enzootic cycle involving passerine birds and mosquitoes that feed on them; passerine birds act as reservoir and amplification hosts. Culiseta melanura is the principal enzootic vector, and human infection can occur through the bite of an infected mosquito. [1]
People in areas where eastern equine encephalitis vectors occur may be exposed through mosquito bites. Risk is greatest during periods of high mosquito activity, generally summer through early fall in temperate areas. [1]
Prevention focuses on reducing mosquito exposure and mosquito populations, including insecticides, larvicides, removal of breeding sites, use of insect repellents, and public education about avoiding mosquito bites. [1]
- 1Wikipedia contributors. Eastern equine encephalitis - Wikipedia [Internet]. Wikipedia. cited 11 Aug 2026.Available from: https://en.wikipedia.org/wiki/Eastern_equine_encephalitis
- 2Baxter VK et al. Genetic control of alphavirus pathogenesis. Mamm Genome. 2018 Aug. PMID: 30151711. doi: 10.1007/s00335-018-9776-1.PubMed: https://pubmed.ncbi.nlm.nih.gov/30151711/
- 3Aksamit AJ Jr et al. Treatment of Viral Encephalitis. Neurol Clin. 2021 Feb. PMID: 33223083. doi: 10.1016/j.ncl.2020.09.011.PubMed: https://pubmed.ncbi.nlm.nih.gov/33223083/
- A83.2
- 1D45
Coverage
Reporting countries and regions
Trends by reporting country
Monthly patterns over time
Data access
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Official sourcesAuthority, cadence, notes1
JP NIID Weekly
Japan
Japan weekly infectious disease surveillance via NIID/JIHS.