West nile virus
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WNV is an enveloped positive-sense ssRNA virus of 11000 base pairs (bp) that is considered a member of the Japanese encephalitis serocomplex. It belongs to the genus Flavivirus and family Flaviviridae. Its RNA encodes structural and non-structural proteins. Although 7 lineages of WNV have been described, only lineage 1 and 2 are clinically significant. The viral natural reservoir includes many species, such as humans, horses, dogs, and cats; but the main natural reservoir is birds.
Viruses; ssRNA viruses; ssRNA positive-strand viruses, no DNA stage; Flaviviridae; Flavivirus; Japanese encephalitis virus group
WNV is a member of Japanese encephalitis serocomplex and belongs to the genus Flavivirus, family Flaviviridae. Other species of the this serocomplex include the St Louis encephalitis virus and the Japanese encephalitis virus.
The WNV has an icosahedral symmetry, with a smooth surface. It is an enveloped virus with a nucleocapsid core built of RNA and capsid proteins. Its genome is contained in a single-stranded RNA of about 11000 bp. It contains a single open reading frame (ORF), a 5' untranslated region (UTR), and another 3' region which is also not translated. The ORF contains a single polyprotein that produces 3 smaller types of structure proteins and 7 of non-structural proteins following processing and translation.
- Structural proteins are responsible for the formation of the viral particle and include:
- Envelope proteins
- Membrane proteins
- C proteins
- Non-structural proteins are responsible for viral replication, evasion of the immune system, and assembly of virions. They include:
The WNV may be classified in 7 phylogenetic lineages. Of these, only 1 and 2 have been identified as causative agents of disease in humans and are considered clinically significant.
- Lineage 1: Widespread, isolates from Europe, America, Middle East, India, Africa, and Australia
- Lingeage 2: Southern Africa, Madagascar, and Europe
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- "Public Health Image Library (PHIL)".