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Avian influenza is an infectious disease of birds
caused by type A strains of the influenza virus. These
flu viruses occur naturally among birds. All birds
are thought to be susceptible to infection with avian
influenza, though some species are more resistant
to infection than others. The disease, which was first
identified in Italy more than 100 years ago, occurs
worldwide.
Avian influenza viruses do not normally infect species
other than birds and pigs. Although avian influenza
A viruses usually do not infect humans, more than
100 confirmed cases of human infection with avian
influenza viruses have been reported since 1997. Most
cases of avian influenza infection in humans are thought
to have resulted from direct contact with infected
poultry or contaminated surfaces. To
date, there have been no cases of avian influenza
A (H5N1) in the United States. For
an In-Depth look on Avian Influenza, click here >>
 Avian
flu fact sheet
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Animal Health
Human Health
A pandemic is a global disease outbreak. An influenza
pandemic occurs when a new influenza A virus emerges
for which there is little or no immunity in the human
population, begins to cause serious illness and then
spreads easily person-to-person worldwide.
Historically, the 20th
century saw 3 pandemics of influenza:
- 1918 influenza pandemic caused at least 500,000
U.S. deaths and up to 40 million deaths worldwide
- 1957 influenza pandemic caused at least 70,000
U.S. deaths and 1-2 million deaths worldwide
- 1968 influenza pandemic caused about 34,000 U.S.
deaths and 700,000 deaths worldwide
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