Flaviviruses constitute a family of linear, single-stranded RNA(+) viruses. Flaviviruses include the West Nile virus, dengue virus, Tick-borne Encephalitis Virus, Yellow Fever Virus, and several other viruses. Many flavivirus species can replicate in both mammalian and insect cells. Most flaviviruses are arthropod borne and multiply in both vertebrates and arthropods. The viruses in this family that are of veterinary importance include Japanese encephalitis virus, St. Louis encephalitis virus, West Nile virus, Israel turkey meningoencephalomyelitis virus, Sitiawan virus, Wesselsbron virus, yellow fever virus and the tick-borne flaviviruses e.g. louping ill virus.