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An RNA virus is a virus that has RNA (ribonucleic acid) as its genetic material.[1] This nucleic acid is usually single-stranded RNA (ssRNA) but may be double-stranded RNA (dsRNA).[2] The ICTV classifies RNA viruses as those that belong to Group III, Group IV or Group V of the Baltimore classification system of classifying viruses, and does not consider viruses with DNA intermediates as RNA viruses.[3] Notable human diseases caused by RNA viruses include SARS, influenza and hepatitis C. Another term for RNA viruses that explicitly excludes retroviruses is ribovirus.[4] RNA viruses can be further classified according to the sense or polarity of their RNA into negative-sense and positive-sense, or ambisense RNA viruses. Positive-sense viral RNA is identical to viral mRNA and thus can be immediately translated by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA polymerase before translation. As such, purified RNA of a positive-sense virus can directly cause infection though it may be less infectious than the whole virus particle. Purified RNA of a negative-sense virus is not infectious by itself as it needs to be transcribed into positive-sense RNA. Ambisense RNA viruses resemble negative-sense RNA viruses, except they also translate genes from the positive strand.[5] The double-stranded (ds)RNA viruses represent a diverse group of viruses that vary widely in host range (humans, animals, plants, fungi, and bacteria), genome segment number (one to twelve), and virion organization (T-number, capsid layers, or turrets). Members of this group include the rotaviruses, renowned globally as the commonest cause of gastroenteritis in young children, and bluetongue virus [6] [7], an economically important pathogen of cattle and sheep. In recent years, remarkable progress has been made in determining, at atomic and subnanometeric levels, the structures of a number of key viral proteins and of the virion capsids of several dsRNA viruses, highlighting the significant parallels in the structure and replicative processes of many of these viruses. [2]
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Positive-sense Ssrna Virus Subcategories
Positive-sense Ssrna Virus Articles
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