The new strain of flu--"do not call it swine flu, call it H1N1," the pork lobby insists, "since you can't get it from eating bacon or ham"--is an unusual, triple hybrid virus, composed not only of swine RNA, but bird and human RNA, as well.
Newsweek, reporting on the origins of H1N1 in its May 11/May 18 issue, says the first case of H1N1 was discovered around Thanksgiving 2005, when a 17-year old boy helped butcher 31 pigs at a Wisconsin slaughterhouse. A week later the teen killed another pig, the magazine reported.
In early December, in preparation for Christmas, his family bought a chicken and kept it in the house, to protect it from the fierce Wisconsin winter. On December 7, the teenager contracted flu. His illness lasted three days and he fully recovered, without spreading it to anyone around him. The virus was the first known case of H1N1, Newsweek says. (See the post below from the Wisconsin Department of Health regarding this case.)
Nine months ago, the Texas Department of State Health Services reported another case to the CDC. An individual who was exposed to infected pigs contracted a virus and was well within a few days.
CDC researchers found the same virus that infected the Wisconsin teenager, Newsweek reports.
In March of this year, the number of influenza cases in Mexico suddenly jumped.
Replication and Reassortment
Scientists say the new influenza strain is a continually mutating microbe, whose genetic code is in the form of RNA. (While some viruses use DNA cells to grow, this one uses RNA.)
The virus invades animals by attaching itself to a receptor in the nose or throat. The virus is then engulfed by a host cell, where its chromosomes reproduce, enter the bloodstream and spread throughout the body. While the virus is spreading, other genetic material may also be enveloped into the thousands of viral cells being copied. For example, if the virus is replicating inside a human cell, it will pick up human genetic material as well as avian genes from a chicken and swine RNA when it enters a pig.
When two types of flu virus get into an animal cell at the same time, they trade entire chromosomes. This is called reassortment and may be the major culprit in generating new strains of viruses.
Viruses spread through coughs or sneezes, though the majority of viruses don't adapt to their host and die. That's why it's rare when a new strain of virus is discovered.
What was infecting the teenager who slaughtered pigs in Wisconsin was a triple reassortment; he was infected with genes from three species of animals: pigs, birds and human beings.