Japanese encephalitis in two children--United States, 2010.

Japanese encephalitis virus (JEV) is the leading cause of vaccine-preventable encephalitis in Asia and the western Pacific. JEV is maintained in an enzootic cycle involving mosquitoes and amplifying vertebrate hosts, mainly pigs and wading birds. The virus is transmitted to humans primarily by Culex mosquitoes, which breed in flooded rice fields and pools of stagnant water and most often feed outdoors during the evening and night. JEV transmission occurs mainly in rural agricultural areas, but occasional human cases occur in urban areas. Japanese encephalitis (JE) in persons who have traveled or lived overseas is diagnosed infrequently in the United States, with only four cases identified from 1992 (when a JE vaccine was first licensed in the United States) to 2008. This report describes the only cases diagnosed in the United States and reported to CDC since then. The first was a fatal case in a U.S. child who had visited relatives in the Philippines. The other occurred in a refugee who became ill while traveling from Thailand to the United States and whose diagnosis was complicated by concurrent neurocysticercosis. JE should be considered in the differential diagnosis for any patient with an acute neurologic infection who recently has been in a JE-endemic country. Travelers to JE-endemic countries should be advised of the risk for JE and the importance of personal protective measures to prevent mosquito bites. JE vaccine should be considered for travelers who might be at greater risk based on the season, location, and duration of their visit and their planned activities.