How can variation and compeition apply to viruses?

Question

Darwin observed that all organisms vary and there is competition between offspring. However, most scientists don’t consider viruses to be living things. How can variation and competition apply to viruses?

Answer 1

The influenza (flu virus) vaccine needs to change EVERY FLU SEASON. This is because of "antigenic drift and shift", meaning the antigens on the virions change (especially hemagglutinin and neuraminidase antigens). This is variation and survival of the fittest, the ones with the old hemagglutinin and neuraminidase antigens were destroyed by immune systems that recognized them.