Avian influenza was first recorded in Italy in 1878. The disease, originally known as Fowl Plague, continuously caused massive outbreaks in poultry, including two outbreaks in the United States (1924 and 1929). In 1955, it was discovered that the virus causing Fowl Plague was an influenza virus.
There are three types of influenza virus: A, B, and C. All influenza viruses affecting domestic animals (horses, pigs, poultry, etc.) belong to type A, which is the most common virus type producing serious epidemics in humans. Influenza types B and C affect only humans.
Avian influenza outbreaks occur sporadically throughout the world. This disease has been very disruptive to the poultry industry; millions of chickens, geese, and turkeys have been destroyed to prevent further spread of the disease
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Starting in 1997, when highly pathogenic avian influenza (HPAI) H5N1 was discovered in humans in Hong Kong, the virus (also known as bird flu) has received unprecedented publicity. The avian influenza outbreak has since spread to 15 countries in Asia, Africa, and the Middle East, and, as of December, 2011, infected 573 people. Three hundred and thirty-six of those infected people died.
Millions of birds have also died or been culled to prevent further spread of the virus. Although the number of people infected with avian influenza is relatively few compared to seasonal human flu, the percentage of people who die from HPAI H5N1 is very high (approximately 60%).
Public health officials are concerned that HPAI H5N1 could mutate into a form that could spread from human to human. Currently, human outbreaks and deaths have resulted mainly from direct contact with infected birds.