What is avian influenza?
Avian influenza, commonly called bird flu, is caused by influenza A viruses that mainly affect birds. Wild aquatic birds are natural hosts for many strains and may carry a virus without appearing seriously ill. Some strains can cause severe disease in poultry, captive birds and wildlife.
The virus may spread through direct contact with infected birds and through saliva, respiratory secretions and droppings. Contaminated water, food, footwear, clothing, cages, tools and vehicles can also move infectious material between locations.
Is bird flu man-made?
No. Avian influenza viruses occur naturally and have circulated in bird populations for a very long time. Like other influenza viruses, they change as they reproduce and exchange genetic material. Scientists study these viruses in laboratories so they can understand outbreaks, improve surveillance and develop tests and vaccines; laboratory study does not mean the disease itself was created by people.
How long has it been known?
A severe bird disease historically called “fowl plague” was described in 1878 and was later identified as influenza. The H5N1 strain that became a major international concern was first identified in farmed geese in southern China in 1996. Different avian influenza strains and lineages have continued to evolve and spread since then.
