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|Avian Influenza "Bird Flu" Factsheet|
Infected birds can shed influenza virus in their saliva, nasal secretions and feces. Domesticated birds may become infected with the AI virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus.
Because all influenza viruses have the ability to change, scientists remain concerned that HPAI H5N1 viruses have the potential to possibly change into a form of the virus that is able to spread easily from person to person. Experts around the world continue to monitor for potential changes in the virus and changes in patterns of human infection.
In 2001 and 2002, H5N1 HPAI re-emerged in poultry in Hong Kong. Roughly 2.5 million birds were killed during these two years to prevent the spread of the virus.
Also in 2001, the H5N1 HPAI virus was isolated from duck meat imported by China by the National Veterinary Research and Quarantine Bureau (South Korea). In a laboratory setting, this virus infected ducks but caused no clinical disease. However, in chickens this virus caused 100 percent mortality.
From December 2002 to February 2003, wild and captive birds infected with H5N1 HPAI virus were discovered dead in two parks in Hong Kong. In the lab, this virus caused high mortality in ducks, chickens, turkey and other gallinaceous poultry species.
In January/February 2003, a family from Hong Kong visiting relatives in China developed respiratory disease. Two died and three were hospitalized. H5N1 influenza A virus was isolated from two family members.
On December 15, 2003, H5N1 HPAI was diagnosed in South Korea in broiler breeder chickens. On January 8, 2004, H5N1 HPAI was diagnosed in Vietnam in broiler breeder chickens. Additional virus discoveries were made in Japan, Thailand, Cambodia and Indonesia in late January 2004. The disease was discovered for the first time in Malaysia in mid-August 2004.
Transmission from bird-to-human can be prevented to a large degree by limiting exposure to live poultry.
The H5N1 HPAI virus is not present in poultry or other birds on European, African, Australian and North and South American continents.
Prevention and the search for a vaccine
Because there are 15 different subtypes of AI viruses, a broadly protective vaccine program is cost prohibitive. However, because three outbreaks of H5N1 HPAI have occurred in Hong Kong, some vaccinations are now required in that country for live poultry. Preventing exposure to AI viruses is the most widely used control strategy.