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
