Fact Sheet: Arboviral Encephalitis
CLINICAL FEATURES
- Aseptic meningitis or encephalitis. Many cases have only fever with headache
- Can progress to focal paralysis, intractable seizures, coma and death
ETIOLOGIC AGENT
- Several alpha-, flavi- and bunya- viruses; chiefly, St. Louis encephalitis (SLE), western equine encephalitis (WEE), Venezuelan equine encephalitis (VEE), eastern equine encephalitis (EEE), LaCrosse virus and other California serogroup viruses
INCIDENCE
- Varies with occurrence and intensity of epidemic transmission; usually 150-3,000 cases/year
SEQUELAE
- Neurologic sequelae in 30% of EEE cases; 10% of SLE cases
- Case fatality rate of 30% in EEE cases; 5% of SLE cases
COSTS
- $150 million - includes estimated cost of vector control and surveillance activities
TRANSMISSION
- Chiefly mosquito-borne
RISK GROUPS
- SLE - elderly; low income areas
- LaCrosse encephalitis - children
- WEE - rural residents of the West
SURVEILLANCE
- Active surveillance in collaboration with state and local health departments, and mosquito control districts
TRENDS
- Changes in lifestyle, emphasizing outdoor activity and "natural" residential locations increase risk of exposure
CHALLENGES
- Infrequent but unpredictable epidemics
- Surveillance methods not adequately sensitive or not utilized
- Develop more effective surveillance, prevention and control strategies
- Control methods impractical
- Control methods not fully evaluated
- Prevention tools limited
- No human vaccines available
- Treatment not always effective
- Knowledge of geographic distribution incomplete
OPPORTUNITIES
- Evaluate natural cycle indices of virus activity and develop surveillance systems that predict epidemic transmission
- Develop and evaluate public health education and intervention strategies
RESEARCH PRIORITIES
- Develop predictive, standardized national surveillance system
- Improve techniques to survey natural transmission cycles
- Improve laboratory diagnostic assays
- Evaluate vector control modalities
- Evaluate infection prevention approaches
- Improved diagnostic tests
- Develop and evaluate vaccines
