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Flaviviridae

Flaviviridae
Virus classification e
(unranked): Virus
Phylum: incertae sedis
Class: incertae sedis
Order: incertae sedis
Family: Flaviviridae
Genera

Flaviviridae is a family of viruses. Humans and other mammals serve as natural hosts. They are primarily spread through arthropod vectors (mainly ticks and mosquitoes). The family gets its name from the yellow fever virus, the type virus of Flaviviridae; flavus means yellow in Latin, and Yellow fever in turn was named because of its propensity to cause jaundice in victims.[1] There are currently over 100 species in this family, divided among four genera.[2][3] Diseases associated with this family include: hepatitis (hepaciviruses), hemorrhagic syndromes, fatal mucosal disease (pestiviruses), hemorrhagic fever, encephalitis, and the birth defect microcephaly (flaviviruses).[3][4]

Taxonomy

This family has four genera and a number of unclassified species.[2][3]

Group: ssRNA(+)

[3]

Unclassified

Other flaviviruses are known that have yet to be classified. These include the Wenling shark virus.

There are a number of viruses that may be related to the flaviviruses but have features that are atypical of the flaviviruses. These include Citrus jingmen-like virus, Guaico Culex virus, Jingmen tick virus, Mogiana tick virus, Soybean cyst nematode virus 5, Toxocara canis larva agent, Wuhan cricket virus and possibly Gentian Kobu-sho-associated virus.

Genome

Flaviviridae have monopartite, linear, single-stranded RNA genomes of positive polarity, 9.6 to 12.3 kilobase in length. The 5'-termini of flaviviruses carry a methylated nucleotide 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.

Virion structure

Virus particles are enveloped, with icosahedral and spherical geometries, about 40–60 nm in diameter.[3][4]

Genus Structure Symmetry Capsid Genomic arrangement Genomic segmentation
Hepacivirus Icosahedral-like Pseudo T=3 Enveloped Linear Monopartite
Flavivirus Icosahedral-like Pseudo T=3 Enveloped Linear Monopartite
Pegivirus Icosahedral-like Pseudo T=3 Enveloped Linear Monopartite
Pestivirus Icosahedral-like Pseudo T=3 Enveloped Linear Monopartite

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral envelope protein E to host receptors, which mediates clathrin-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 virus exits the host cell by budding. Humans and mammals serve as the natural host. The virus is transmitted via a vector (ticks and mosquitoes).[3][4]

Genus Host details Tissue tropism Entry details Release details Replication site Assembly site Transmission
Hepacivirus Humans Epithelium: skin; epithelium: kidney; epithelium: intestine; epithelium: testes Clathrin-mediated endocytosis Secretion Cytoplasm Cytoplasm Sex; blood
Flavivirus Humans; mammals; mosquitoes; ticks Epithelium: skin; epithelium: kidney; epithelium: intestine; epithelium: testes Clathrin-mediated endocytosis Secretion Cytoplasm Cytoplasm Zoonosis; arthropod bite
Pegivirus Mammals None Clathrin-mediated endocytosis Secretion Cytoplasm Cytoplasm Unknown
Pestivirus Mammals None Clathrin-mediated endocytosis Secretion Cytoplasm Cytoplasm Vertical: parental

Clinical importance

Major diseases caused by the Flaviviridae family include:

References

  1. ^ "Flaviviridae". Microbe Wiki. Retrieved July 22, 2008.
  2. ^ a b Simmonds, P; Becher, P; Bukh, J; Gould, E; Meyers, G; Monath, T; Muerhoff, S; Pletnev, A; Rico-Hesse, R; Smith, D; Stapleton, J; ICTV Report Consortium (2017). "ICTV Virus Taxonomy Profile: Flaviviridae". Journal of General Virology. 98: 2–3. doi:10.1099/jgv.0.000672.
  3. ^ a b c d e f "Flaviviridae". ICTV Online Report.
  4. ^ a b c "Viral Zone". ExPASy. Retrieved 15 June 2015.

External links