InfluenzaSwine flu , now known as the 2009 H1N1 flu, is caused by the orthomyxovirus which usually affects pigs but viral mutations allows the virus to cross species to other hosts like humans. The swine influenza virus (SIV) is another example of cross species viral infection which was previously seen with other Zoonotic infections like in civets to humans SARS or Sudden Acute Respiratory Syndrome and from birds to humans as seen with avian (bird) flu.
Unlike SARS and bird flu, swine flu has mutated to the point where the virus can now spread from human-to-human. This current mutation is the cause of the global scare of the recent 2009 outbreak which is feared to become a pandemic. With the popularity of air travel, infected passengers from one region can easily travel to other nations and result in new outbreaks occurring in regions that were not prone to swine flu.
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