Japanese encephalitis in a U.S. traveler returning from Thailand, 2004.

Japanese encephalitis (JE) virus is a mosquito-borne flavivirus that is closely related to the West Nile and St. Louis encephalitis viruses endemic to North America. JE virus is a leading cause of viral encephalitis in Asia but is rarely reported among travelers to countries where JE is endemic. This report describes a case of an unvaccinated Washington resident who had JE after traveling to northern Thailand. The Advisory Committee on Immunization Practices (ACIP) recommends JE vaccine for travelers to JE-endemic areas of Asia during the transmission season, especially those spending > or =1 month in those areas and whose travel itineraries include rural settings. JE vaccine should also be considered for travelers visiting areas with epidemic transmission or those engaging in extensive outdoor activity in rural settings in areas where JE is endemic, regardless of the duration of their visit. In addition, health-care providers and organized international travel programs should ensure that travelers obtain appropriate preventive health guidance before travel.