The flu is caused by one of three viruses: A, B, and C. Types A and B cause epidemics. Type A virus also has strains A (H1N1) and A (H3N2). Further more, in 2009 type A (H1N1) has developed into a new type A (H1N1) which according to the CDC “caused the first influenza pandemic in more than 40 years.”[1] The flu vaccine includes the type A (H1N1), A(H3N2), and type B. Next year’s vaccine will also contain the year 2009’s H1N1 virus.
Virus Mutation
New types of virus develop in two ways. One way is gradual and occurs over time. This is called an “antigenic drift”. As the human body develops antibodies against one virus, it mutates and the body becomes infected with the new virus. Hence, in order to be “protected” from the flu one must (indefinitely) get the new and improved flu shot every year. Type B virus changes this way only.
The "antigenic shift" is caused by an abrupt change in the virus and “ has emerged from an animal population that is so different from the same subtype in humans that most people do not have immunity to the new (e.g. novel) virus” [2] as according to the CDC. These shifts create the more dangerous flu viruses such as the 2009 H1N1 virus and occur occasionally.
Swine and avian flu
Animals such as chickens and pigs carry the type A viruses. Wild birds are considered to be “the primary natural reservoir for all subtypes of influenza A viruses and are thought to be the source of influenza A viruses in all other animals.” Pigs can be simultaneous carriers for avian, human, and swine viruses. This is when and how these viruses can become genetically altered to include properties of each. This was partially the case with the “swine flu” of 2009.
Come back soon for information on the flu shot, related statistics, and the Green Living way of dealing with the flu.
References
[1], [2], [3]. http://www.cdc.gov/flu/about/viruses/index.htm
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