health

Avian influenza, or bird flu, is a form of flu caused by a strain of the influenza
A virus that ordinarily affects only birds. Avian influenza is considered
a zoonosis because it can be transmitted from animals to humans.
It is also considered an emerging disease because it has been identified
as a major public health problem within the last twenty years and threatens
to get worse in the near future.
Wild birds carry many types of the influenza A virus in their digestive
tract but do not usually get sick from it. Infected wild birds can, however,
infect chickens, turkeys, and other domesticated birds through contact
with their nasal secretions or droppings. The infection can be spread by
contaminated bird feed, water, or soil as well as by direct contact between
wild birds and domesticated poultry.
There are two subtypes of avian flu in birds:
a relatively mild form that causes symptoms such as feather loss and
a severe form that can kill entire flocks of chickens, geese, or turkeys
within forty-eight hours.
Most cases of avian flu in humans as of 2008 have occurred in farmers
or other people who were exposed to sick birds. There are very
few cases of human-to-human transmission of this form of influenza.
The primary reason for concern is that one specific form of the flu virus
that causes avian flu—H5N1—could cause widespread sickness and death
if it mutates into a form that can spread easily and directly from
human to human. It was a different form of the influenza A virus (H1N1)
that caused the flu pandemic of 1918–1920, which took the lives
of millions of people worldwide.