Japanese encephalitis virus is an arbovirus (arthropod-transmitted virus) in the
genus Flavivirus and family Flaviviridae. There is only one serotype but there are two
subtypes of the virus (Nakayama and JaGar–01). Viral strains can also be grouped
into four or perhaps five genotypes.
Japanese encephalitis virus is closely related to St. Louis encephalitis virus,
Murray Valley encephalitis virus and West Nile virus; these viruses and a few others
comprise the Japanese encephalitis serogroup of the flaviviruses.