The Grim Tale
Influenza is likely to have had an avian origin. In waterfowl,
influenza is always asymptomatic and birds regularly shed large
amounts of the virus. They seldom get sick, while other small
mammals that contract the influenza virus are infected and may die.
It appears that birds have established a coexistance with the
influenza virus. Through evolution, birds and the influenza virus are optimally
adapted to one another. Currently the avian influenza gene pool has
reached evolutionary stasis, while mammal oriented influenza is
constantly evolving to avoid host defenses.
The first mammal to be diagnosed with the influenza virus was the
horse. Most of the mammalian strains of the virus found today
date back at least one hundred years and some subtypes date back
a few centuries. All present day human influenza subtypes appeared
just before 1918, the year of the worst pandemic.
A timeline of influenza strains beginning in 1890 to 1990
[ Influenza HomePage ] - [ What is Influenza ]
[ Antigenic Drift ] - [ Replication ]
[ Past Pandemics ] - [ Prevention and Treatment ]
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Last modified: 4/24/98