How easy is it for humans to catch influenza viruses from animals?
It is usually much more difficult for an animal type of influenza to infect a human, than it is for a human influenza type to infect a human. This is because the human types are much better adapted to the human body. However, the current situation with the new human swine influenza virus is that it contains gene segments from swine influenza and human influenza. This means that it has increased ability to infect humans. Pigs are able to be infected with swine flu types, human types and bird types of influenza. The different viruses swap their genes when inside infected pigs and a new virus, which is a mix of swine, human or avian influenza can then emerge.
