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 ]
[ Bibliography & Other Links ]

email: David Zage

Last modified: 4/24/98