Infection with the flu virus H7N9 is normally confined to poultry birds - but it was first found to have infected a human in March 2013, going on to cause 132 infections in people during that spring, and leading to 44 deaths.1,2The H7N9 virus is an avian influenza. The bird flu does not usually cross to humans, and when zoonosis does occur, it is a rare event.3Because humans have not developed immunity to these subtypes of flu virus - which are continually evolving - the infections they cause us can be severe and life-threatening.

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