Influenza virus APR834H1N1 FLUA

Type species of the genus Influenzavirus A, isolated from a case of influenza in Puerto Rico in 1934.

Influenzavirus B (FLUBV) A genus of the family Orthomyxoviridae consisting of one species: Influenza virus B, the members of which infect only humans. The virus is defined by the possession of ribonucleo-protein antigen B. Human strains in this genus are described according to a convention which sets out information in the following order: (1) antigen B; (2) geographical region; (3) isolation number; (4) year of isolation. Example: B/ Yamagata/16/88. All strains share a common NP and M protein. There is no M2 protein, but an analogous protein (NB) is encoded by RNA segment 6. In contrast to influenzaviruses A, no distinct antigenic subtypes are recognized for influenzavirus B, and antigenic drift occurs more slowly. There is no antigenic shift. Influenzaviruses B can readily reassort gene segments between each other, but no reassortment has been found with influenzaviruses A. The only natural host is humans. Causes sporadic and epidemic respiratory disease, usually milder than that caused by Influenza A. Ferrets can be infected experimentally causing mild disease or none at all. Strains have been adapted to produce pneumonia in mice. The virus is easily propagated in eggs and in monkey kidney cell cultures. Laboratory strains grow with CPE in human amnion, pig, calf and ferret cells.

Influenzavirus C (FLUCV) A genus in the family Orthomyxoviridae, the members of which naturally infect humans causing mild, sporadic respiratory disease. The type species is influenza C/ California/78. Its genome has only seven segments. A

single envelope protein, the hemagglu-tinin-esterase-fusion (HEF) protein is present on the virion surface, but there is no neuraminidase. All strains of the genus share a common ribonucleoprotein antigen, the NP protein. The HEF protein distinguishes antigenic variants of the genus, and antibody to HEF protein neutralizes infectivity. Differs from influenzavirus A in the virion having a lower density (1.17-1.19g/ml). Isolated in the amniotic cavity of embryonated eggs. Replicates in canine kidney cell line (MDCK), best in presence of trypsin (20g/ml). Infections usually occur in children. A similar virus is also reported to infect swine in China.

Herrler G and Klenk H-D (1991) Adv Virus Res 40, 213

Nakada S et al (1984) Virus Res 1, 433

influenza virus D Synonym for Human parainfluenza virus type 1.

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