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.1,2
The 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.3
Because 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.3
Another avian flu virus has crossed over from bird populations to spread among humans - it was the H5N1 bird flu that first broke out in 1997.3 It caused severe respiratory illness and death, and continues to circulate around poultry in parts of Asia and north-east Africa.4
Whenever a new type of bird flu infection is reported in a person, fears are soon raised that it could be deadly, too. The concerns come in three stages:
- Does the new virus subtype cross easily from birds to humans?
- How bad is the illness when the virus infects a person?
- Will the virus spread quickly and widely among human populations?
As soon as new reports emerge, researchers and governments swing into action to start identifying and tracking the new flu virus, the aim being to maximize the chances of containing any potential epidemic. An international body is at the center of this effort, called the Global Early Warning System (GLEWS), which coordinates disease surveillance work by bodies including the World Health Organization (WHO).
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