Avian flu has been around for a long time in wild birds. It started getting noticed by poultry farmers as far back as the early 1900s.
But the potent flu virus known as H5N1 wasn't discovered until 1997, when it suddenly surfaced on a goose farm in China. H5N1 attracted attention because birds became sick so swiftly, and such a great many died. Since that time, H5N1 has spread to over 60 countries in Asia, Africa, and Europe.
There are a few direct and indirect ways for H5N1 to spread once it strikes a domestic flock of birds. But how is the virus introduced to commercial poultry in the first place? Often it comes from migratory wild waterfowl such as ducks or geese, who can carry the virus from place to place without getting sick themselves. That's why scientists often call these wild birds "reservoirs" for the virus.
H5N1 in humans
Most of the time, H5N1 has been found only in birds. However, in some regions, especially where humans and domestic birds are in very close contact, people have become sick with H5N1 as well.
Occasionally, a person infected with avian flu has passed it on to someone else. In 2004 in Thailand, a mother caught H5N1 from her sick child. In 2006 in Indonesia, eight family members became ill with H5N1 after just one person in the family came into contact with infected poultry.
Bird outbreaks are not expected to slow down in those regions anytime soon. But while avian flu has turned up in Canada from time to time, to date the H5N1 subtype that's circulating through those overseas countries has not been found here. Our government is taking many precautions in an effort to keep it that way.
The future of avian flu
Although H5N1 hasn't yet evolved into a virus that can spread easily among people, scientists have found a few small differences in newer strains. Some of the H5N1 strains that are circulating right now are becoming better at spreading disease among animals. Some domestic birds may now be carrying the virus without showing any symptoms.
Since viruses are masters at mutating, we can be sure we haven't seen the last of these kinds of shifts.
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