! style="background: violet;" | Virus classification
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Flavivirus is a genus of the family Flaviviridae. This complex includes the West Nile virus, dengue virus, Tick-borne Encephalitis Virus, Yellow Fever Virus, and several other viruses which cause encephalitis.
Flavivirus share a common size (40-60 microinches), symmetry (enveloped, icosahedral nucleocapsid), nucleic acid (positive-sense, single stranded RNA approximately 10,000-11,000 bases), and appearance in the electron microscope.
Flavivirus have a (+) sense RNA genome and replicate in the cytoplasm of the host cells. The genome mimics the cellular mRNA molecule in all aspects except for the absence of the poly-adenylated (poly-A) tail. This feature allows the virus to exploit cellular apparatus to synthesise both structural and non-structural proteins, during replication. The cellular ribosome is crucial to the replication of the flavivirus, as it translates the RNA, in a similar fashion to cellular mRNA, resulting in the synthesis of a single polyprotein.
Once translated, the polyprotein is cleaved by a combination of viral and host proteases to release mature polypeptide products. Nevertheless, cellular post-translational modification is dependent on the presence of a poly-A tail; therefore this process is not host-dependent. Instead, the polyprotein contains an autocatalytic feature which automatically releases the first peptide, a virus specific enzyme. This enzyme is then able to cleave the remaining polyprotein into the individual products. One of the products cleaved is a polymerase, responsible for the synthesis of a (-) sense RNA molecule. Consequently this molecule acts as the template for the synthesis of the genomic progeny RNA.
New viral particles are subsequently assembled. This occurs during the budding process which is also responsible for the accumulation of the envelope and cell lysis.
- Genus Flavivirus
- Tick-borne viruses
- Mosquito-borne viruses
- Aroa virus group
- Dengue virus group
- Japanese encephalitis virus group
- Kokobera virus group
- Ntaya virus group
- Spondweni virus group
- Yellow fever virus group
- Viruses with no known arthropod vector