As flu-watchers like to say, you can always count on influenza virus to surprise.
The is that scientists have apparently been wrong about where new flu viruses come from. The dogma is that they always incubate in wild migratory birds, then get into domestic poultry, and then jump into mammals — especially pigs and humans.
If novel flu viruses acquire the ability to transmit readily in humans — boom! — you’ve got a pandemic on your hands. And if a pandemic virus is particularly lethal, like the that has made public health people anxious for the past 10 years, it could be a global catastrophe.
But evolutionary biologist and his colleagues say that wild-bird scenario does not describe the true origin of the flu viruses that have troubled the world over the past 140 years.
Instead, the flu viruses circulating globally since the early 1870s are all closely related to those that infect an animal we don’t associate with influenza these days: the horse.
Worobey, of the University of Arizona, has reanalyzed 80,000 flu virus genomes with a new set of assumptions about how these viruses mutate at widely different rates when they infect different species. His team found there was a “global sweep” in the mid-19th century that replaced six of the flu viruses’ eight genes — the “internal” genes that code for proteins other than the hemagglutinin and neuraminidase markers found on the viruses’ surface.
There’s intriguing evidence that the ancestor of modern flu viruses first appeared in horses — and not that long ago, in evolutionary terms. Its introduction is marked by an that began near Toronto in late 1872 quickly devastated horse populations all over North America.
Horsepower was essential in this pre-internal-combustion-engine era, so there were lots of horses around. And so many horses died of the flu that mail delivery broke down, the price of coal soared (because it couldn’t be delivered), the U.S. cavalry had to fight Apaches on foot, and a fire destroyed half of Boston because teams of young men drafted to pull the pumping trucks couldn’t respond fast enough.
… The new analysis, published online Sunday in Nature, doesn’t determine whether the new flu jumped from horses into poultry or the other way around. Chickens could have picked it up by roosting in barns with sick horses, or vice-versa. But in either case, it’s clear that, once established in domestic birds, it spread to wild birds — ultimately to the world over.
Moreover, that 1870s-vintage virus contributed most of its genes to the H1N1 flu virus that caused the devastating pandemic in 1918-1919, which around the globe.
via Research Shows New Flu Viruses Often Arise In Domestic Animals : Shots – Health News : NPR.