The swine flu has been labeled as H1N1. The strain that killed millions of people in 1918 was also labeled H1N1; is it the same virus?
It is not the same virus. The current strain is a new variation of an H1N1 virus, which is a mix of human and animal versions. H1 refers to type of hemagglutinin, which is involved in the virus gaining entry into a target cell. N1 refers to neuraminidase, an enzyme that allows the release of copies of the virus from infected cells. A new variation can be created when an animal is infected with two or more different viruses at the same time. The viruses can exchange genes. This can be particularly dangerous because people may not have any immune defense against it. You may have heard to this swine flu virus refered to as “Type A.” There are three general types of influenza, Type A, Type B and Type C. Type A occurs in many species and historically has been the sole cause of pandemics.
