| Flaviviridae | |
|---|---|
 | |
| Zika virus virion structure and genome | |
Virus classification | |
| (unranked): | Virus |
| Realm: | Riboviria |
| Kingdom: | Orthornavirae |
| Phylum: | Kitrinoviricota |
| Class: | Flasuviricetes |
| Order: | Amarillovirales |
| Family: | Flaviviridae |
| Genera | |
Flaviviridae, commonlyflavivirus,flaviviral, andflaviviruses,[1] is a family ofenvelopedpositive-strand RNA viruses which mainly infectmammals andbirds.[2] They are primarily spread througharthropodvectors (mainlyticks andmosquitoes).[3] The family gets its name from theyellow fever virus;flavus is Latin for "yellow", and yellow fever in turn was named because of its propensity to causejaundice in victims.[4] There are 89 species in the family divided among four genera.[3] Diseases associated with the group include:hepatitis (hepaciviruses),hemorrhagic syndromes,fatal mucosal disease (pestiviruses),hemorrhagic fever,encephalitis, and the birth defectmicrocephaly (flaviviruses).[5]
Virus particles are enveloped and spherical with icosahedral-like geometries that have pseudo T=3 symmetry. They are about 40–60nm in diameter.[3][5]
 | This section includes a list ofgeneral references, butit lacks sufficient correspondinginline citations. Please help toimprove this section byintroducing more precise citations.(July 2024) (Learn how and when to remove this message) |
Members of the familyFlaviviridae have monopartite, linear, single-strandedRNAgenomes of positive polarity, and 9.6 to 12.3 kilobase in total length. The 5'-termini of flaviviruses carry amethylatednucleotide cap, while other members of this family are uncapped and encode an internal ribosome entry site.
The genome encodes a single polyprotein with multiple transmembrane domains that is cleaved, by both host and viral proteases, into structural and non-structural proteins. Among the non-structural protein products (NS), the locations and sequences of NS3 and NS5, which contain motifs essential for polyprotein processing and RNA replication respectively, are relatively well conserved across the family and may be useful for phylogenetic analysis.
Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral envelope protein E to host receptors, which mediatesclathrin-mediated endocytosis. Replication follows the positive-stranded RNA virus replication model. Positive-stranded RNA virus transcription is the method of transcription. Translation takes place by viral initiation. The virion assembles by budding through intracellular membranes and exits the host cell by exocytosis.[3][5][6]
| Genus | Host details | Tissue tropism | Entry details | Release details | Replication site | Assembly site | Transmission |
|---|---|---|---|---|---|---|---|
| Flavivirus | Humans; mammals; mosquitoes; ticks | Epithelium: skin; epithelium: kidney; epithelium: intestine; epithelium: testes | Clathrin-mediated endocytosis | Secretion | Cytoplasm | Cytoplasm | Zoonosis; arthropod bite |
| Hepacivirus | Humans | Epithelium: skin; epithelium: kidney; epithelium: intestine; epithelium: testes | Clathrin-mediated endocytosis | Secretion | Cytoplasm | Cytoplasm | Sex; blood |
| Pegivirus | Mammals | None | Clathrin-mediated endocytosis | Secretion | Cytoplasm | Cytoplasm | Unknown |
| Pestivirus | Mammals | None | Clathrin-mediated endocytosis | Secretion | Cytoplasm | Cytoplasm | Vertical: parental |
A wide variety of natural hosts are used by different members of theFlaviviridae, including fish, mammals including humans and various invertebrates, such as those specific to mollusks and crustaceans.[7] The genomes of these flaviviruses show closesynteny with that of the flavivirus type species, yellow fever virus.[8] One flavivirus, theWenzhou shark flavivirus, infects bothPacific spadenose sharks (Scoliodon macrorhynchos) andGazami crabs (Portunus trituberculatus) with overlapping ranges, raising the possibility of a two-host marine lifecycle.[7] However, another clade of flavivirus, the insect-specific flaviviruses, have genomes that do not demonstrate strong synteny with any of these groups, suggesting a complex evolutionary history.[3][9]
Flavivirusendogenous viral elements, traces of flavivirus genomes integrated into the host's DNA, are found in many species, including a tadpole shrimpLepidurus articus, the water fleaDaphnia magna and a freshwater jellyfishCraspedacusta sowerbii,[8] suggesting ancient coevolution between animal and flavivirus lineages.[7][8] Many of the well-known members of the family causing disease in vertebrates are transmitted via arthropod vectors (ticks and mosquitoes).[3][5][8]
TheFlaviviridae are part ofRNA virus supergroup II, which includes certain plant viruses and bacterial viruses.[3] In 2022, theInternational Committee on Taxonomy of Viruses (ICTV) discussed in 2022 the common names such as flavivirus, flaviviral, and flaviviruses used for both the family and the genusFlavivirus.[10] As more viruses particularly classified under separate genera became established, the names became confusing. The ICTV therefore resolved in 2023 that the genusFlavivirus should be replaced withOrthoflavivirus and that the common names can be used for the entire family.[1]
The family has four genera:[2][3]
Major diseases caused by members of the familyFlaviviridae include:
| International | |
|---|---|
| National | |
