Avian Influenza A (Bird Flu)
Avian influenza is an influenza virus that is commonly found in wild bird populations. While it is very contagious, most wild birds contain the virus within their intestinal tract and do not generally become sick with it. However, when these populations come into contact with commonly kept domesticated birds such as chickens, turkeys, ducks and geese who are not commonly exposed to the virus, they can become very ill, and infections can turn deadly.
The virus can be transmitted through direct contact with infected birds, and through indirect contact via conatminated surfaces, food or water.
Highly pathogenic forms of the virus can have a very high mortality rate amongst these domestic birds, with reports of 90 to 100% mortality of domestic flocks in 48 hours.
Bird flu is considered to be a zoonotic disease as the virus can jump the species barrier and infect humans. Incidents of human cases of the disease generally coincide with domestic bird outbreaks, although most human cases tend to be mild, as humans are not the principal host to the virus.
However, one strain of the avian flu virus, H5N1, has been found to cause the highest number of human fatalities, when infection does occur, over 50% of the human patients succumbed to the virus. There have been outbreaks of this virus throughout Asia, Africa, the Near East and parts of Europe. All infected individuals have had close contact with infected birds, and there have been few cases of the disease spreading directly from human to human.