What is "flavivirus"

n. animal viruses belonging to the family Flaviviridae

Flavivirus is a genus of viruses in the family Flaviviridae. This genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika virus and several other viruses which may cause encephalitis.

Flaviviruses are named from the yellow fever virus, the type virus for the family; the word flavus means "yellow" in Latin. The name yellow fever originated from its propensity to cause yellow jaundice in victims.

Flaviviruses share several common aspects: common size (40–65 nm), symmetry ( enveloped, icosahedral nucleocapsid), nucleic acid ( positive-sense, single-stranded RNA around 10,000–11,000 bases), and appearance in the electron microscope.

Most of these viruses are transmitted by the bite from an infected arthropod (mosquito or tick) and hence, classified as arboviruses. Human infections with these viruses are typically incidental, as humans are usually unable to replicate the virus to high enough titers to reinfect the arthropods needed to continue the virus lifecycle – man is then a dead end host. The exceptions to this are the yellow fever, dengue, and zika viruses, which still require mosquito vectors, but are well-enough adapted to humans as to not necessarily depend upon animal hosts (although they continue to have important animal transmission routes, as well).

Other virus transmission routes for arboviruses include handling infected animal carcasses, blood transfusion, child birth and through consumption of unpasteurised milk products. The transmission from animals to humans without an intermediate vector arthropod is thought to be unlikely. For example, early tests with yellow fever showed that the disease is not contagious.

The known non-arboviruses of the flavivirus family reproduce in either arthropods or vertebrates, but not both, with one odd member of the genus affecting a nematode.