A systemic infection is. The spikes of influenza virus are designated as a. HA and NA antigens. R and B antigens. A and B antigens. The pathogenesis of influenza typically involves infection of a. lymph nodes.
Antigenic shift is a. a change in the position of antigens on the virus.
Influenza vaccination is recommended yearly because a. Immunity only lasts one year. The composition of the vaccine changes according to the most prevalent strains that are circulating. Vaccine makers wish to make more money. The vaccine decomposes in one year. A serious sequela of measles is a. muscular paralysis.