All About Viruses and Bacteria

Antigenic Drift and Antigenic Shift

Antigenic Shift
   Antigenic shift and antigenic drift are the processes in which viruses mutate over time. Antigenic drift happens slowly over time and is common for most flu viruses; antigenic shift happens quicker but is not as commonly done. First let’s explain antigenic drift. Antigenic drift happens naturally over time and is the reason you need a new seasonal flu vaccine very year. When a virus reproduces it injects it's genes into a host cell. The host cell then makes copies of the genes to make new viruses. In this process a small change is made to the genes either naturally or by mistake. The viruses with slightly new genes are released and the spread. This process happens slowly and does not happen every time a cell reproduces. This can happen slowly between flu seasons. That small change between flu seasons is enough to need a new seasonal flu vaccine. Antigenic shift is different form antigenic drift. It is a quick change of genes and is more complicated. The virus infects a host in a bird. Birds are the natural hosts for the flu, so they are infected first before infecting any other animals. After it infects the bird the virus mutates to infect another animal like a pig or a horse. Them a flu virus that can infect humans also infects the same animal as before. The human virus and the bird virus then both inject their DNA into the small host cell. The DNA mixes and changes around. When the viruses are done being created they leave the host cell and continue on infecting humans, animals, and birds with its newly altered DNA. This shift is very dangerous; if we let this happen, this allows the virus strain to infect humans, animals, and birds. If the virus can quickly spread it could wreak havoc over people and animals. People would quickly die because the virus is mixing genes so much that it is constantly changing. The old antibodies won't work after it mutates, so with a quick spread and no vaccine millions of people could die.

Antigenic Drift