H1N1 Influenza type A viruses are common in many species in many parts of the world. Some of these viruses can be transmitted between species.
To date, the recently identified strain of H1N1 influenza has been found in humans in over 30 countries. This virus was originally referred to as "swine flu" because laboratory testing showed that many of the genes in this new virus were very similar to influenza viruses that normally occur in pigs in North America. But further study has shown that the genetic makeup of this new virus is very different from what normally circulates in North American pigs. It has two genes from flu viruses that normally circulate in pigs in Europe and Asia as well as avian genes and human genes. There is no evidence that this virus originated in swine, nor any evidence that any humans have contracted the virus from swine. For more information, visit the links below.