The Influenza Viruses

Exhibit Installation Photo 04

Influenza virus model from Influenza: Complex Virus/Complex History

The Science Behind Flu Viruses

Most people have had some experience with influenza. Throughout history, influenza viruses have spread across the globe. Influenza viruses are constantly changing, and this, in part, accounts for the influenza viruses' changing appearance.

All influenza viruses undergo frequent genetic changes. Small genetic changes that occur during replication are called “antigenic drift.”1 Another type of change is “antigenic shift,” a major and abrupt change that can occur in influenza A viruses.2 Antigenic shift can result in a new combination of the virus’ surface proteins, hemagglutinin (HA)3 and neuraminidase (NA)4. When antigenic shift happens, most people have little or no immunity against the new virus.

  1. antigenic drift: small changes in the genes of influenza viruses that happen continually over time↩

  2. antigenic shift: an abrupt, major change in an influenza A virus↩

  3. Hemagglutinin: antigen found on the surface of flu viruses that allows the virus to enter a cell↩

  4. Neuraminidase: antigen found on the surface of flu viruses that allows the virus to exit a cell↩

The Influenza Viruses