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Japanese
Encephalitis Fact Sheet
CLINICAL FEATURES
- Acute encephalitis;
can progress to paralysis, seizures, coma and death
- The majority of
infections are subclinical
ETIOLOGIC AGENT
- Japanese encephalitis
(JE) virus: flavivirus antigenically related to St. Louis encephalitis
virus
INCIDENCE
- Leading cause of
viral encephalitis in Asia with 30-50,000 cases reported annually
- Fewer than 1 case/year
in U.S. civilians and military personnel traveling to and living in
Asia
- Rare outbreaks
in U.S. territories in Western Pacific
SEQUELAE
- Case-fatality ratio:
30%
- Serious neurologic
sequela: 30%
COST
- Domestic: <
$1 million/year - largely cost of immunizing travelers and military
personnel
- International:
no data, probably tens of millions of dollars
TRANSMISSION
- Mosquito-borne
Culex tritaeniorhynchus group
RISK GROUPS
- Residents of rural
areas in endemic locations
- Active duty military
deployed to endemic areas
- Expatriates in
rural areas
- Disease risk extremely
low in travelers
SURVEILLANCE
- Passive system
based on domestic imported cases referred to CDC and other reference
laboratories
- Laboratory-based
passive surveillance in endemic areas
TRENDS
- Expanding range
of JE viral transmission to northern Australia
- Inactivated JE
vaccine
CHALLENGES
- Currently available
killed vaccine expensive and occasionally reactogenic
OPPORTUNITIES
- Alternative cheaper,
effective attenuated vaccine used in China, but not available elsewhere
- Post marketing
surveillance of adverse reactions to killed vaccine
- Electronically
available information for travelers and care providers
RESEARCH PRIORITIES
- Facilitate implementation
of attenuated vaccine in unvaccinated populations in endemic areas
- Develop improved
vaccines
- Identify risk factors
for progression to symptomatic encephalitis and viral persistence
- Describe clinical
features of JE in AIDS and determine its potential as an opportunistic
infection
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