Subtypes According to antigenicity of HA and NA, influenza virus is divided into subtypes such as HnNm( hind, et al
16 Subtypes • According to antigenicity of HA and NA, influenza virus is divided into subtypes such as HnNm( H1N2, et al )
Variation and Epidemiology Antigenic drift: median or small epidemic Antigenic shift: large scale epidemic
17 Variation and Epidemiology Antigenic drift: median or small epidemic. Antigenic shift:large scale epidemic
AntigenicshifitOf Influenza virus Reassortment of genes is a common feature of Influenza A, but not。r When two dffferent viruses infect the same cel their ra segments can become mixed during replicati。n New viruses produeed in this way may survive due to a selective advantage within the population 18
18 Antigenic Shift Of Influenza virus • Reassortment of genes is a common feature of Influenza A, but not B or C • When two different "A" viruses infect the same cell, their RNA segments can become mixed during replication • New viruses produced in this way may survive due to a selective advantage within the population
AntigenicDrifitoflniuenalirus Constant mutations in the rnaofinfiluenza which lead to polypeptide mutations Changes are less dramatic than those induced by Shiit If these mutations affect HA or NA they may cause localized epidemics 19
19 Antigenic Drift of Influenza Virus • Constant mutations in the RNA of influenza which lead to polypeptide mutations • Changes are less dramatic than those induced by Shift • If these mutations affect HA or NA they may cause localized epidemics
Haemagglutinin Antigenic (HA) DRIFT neuraminidase [HAY Antigenic SHIFT
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