Type A Influenza Virus And Why The Biology Of This Virus Is A Threat Essay

Type A Influenza Virus And Why The Biology Of This Virus Is A Threat To Human - Essay Example This is of great importance in the epidemiology of the disease. Antigenic variability is highest in influenza virus type A and less in type B, while it has not been demonstrated in type C. The internal RNP antigen and M protein antigen are stable but both the surface antigens, hemagglutinin and neuraminidase, undergo independent antigenic variations, which may be of two types - antigenic shift and antigenic drift. Here, the new antigens, though different from the previous antigens, are related to them, so that they react with the antisera to the predecessor virus strains, to varying degrees. Antigenic drift is due to the mutation and selection, the process being influenced by the presence of antibodies to the predecessor strains in the host population. Antigenic drift accounts for the periodical epidemics of influenza. Antigenic shift, on the other hand, is an abrupt, drastic, discontinuous variation in the antigenic structure, resulting in a novel virus strain unrelated antigenically to predecessor strains. Such changes may involve hemagglutinin, neuraminidase or both. Antibodies to predecessor viruses do not neutralize the new variants and can, therefore, spread widely in the population causing major epidemics or pandemics.