Ecology and geographical expansion of Japanese encephalitis virus.

Japanese encephalitis virus (JEV) (Flavivirus: Flaviviridae) is a leading cause of encephalitis in eastern and southern Asia. The virus is maintained in a zoonotic cycle between ardeid wading birds and/or pigs and Culex mosquitoes. The primary mosquito vector of JEV is Culex tritaeniorhynchus, although species such as Cx. gelidus, Cx. fuscocephala, and Cx. annulirostris are important secondary or regional vectors. Control of JEV is achieved through human and/or swine vaccination, changes in animal husbandry, mosquito control, or a combination of these strategies. This review outlines the ecology of JEV and examines the recent expansion of its geographical range, before assessing its ability to emerge in new regions, using the hypothetical establishment in the United States as a case study.