Avian Influenza (Bird Flu)
Avian (bird) influenza (flu) viruses occur naturally in birds. Wild birds worldwide carry the viruses in their intestines and usually do not get sick from them. However, avian flu can infect domesticated birds, including chickens, ducks and turkeys.
In domestic poultry, there are two main forms of the avian influenza virus. The less severe of the two (“low pathogenic,” LPAI H5N1) commonly causes only mild symptoms (ruffled feathers, a drop in egg production) and may easily go undetected. The more severe form (highly pathogenic, HPAI H5N1) spreads very rapidly through poultry flocks, causes disease affecting multiple internal organs, and has a mortality rate that can approach 100%, often within 48 hours.
On rare occasions, bird flu viruses can infect humans. The risk is generally low to most people. However, confirmed cases of human infection have been reported since 1997.
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