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Apr 28, 2009 10:45 pm US/Central
Good Question: How Does Flu Go To Animal To Human?
(WCCO)
From avian flu to swine flu, influenza has a history of jumping from animals to humans. But how does the flu mutate to go from a pig to a person?
"What's interesting and important to note about influenza viruses, is that they're shared viruses between humans and mammals, animals, like pigs, and birds," said Marie Gramer, Ph.D., a researcher at the University of Minnesota's Veterinary Diagnostic Center.
Influenza is a zoonotic, in that it spreads from animals to humans. According to the World Health Organization, about 60 percent of pathogens travel from animals to humans, things like salmonella and rabies.
The flu works both ways, constantly changing.
"The virus is going to change or it'll be attacked by the immune system. So for the virus to survive it has to change or it's always going to get attacked," said Gramer.
When two different strains of the flu virus come together they can change, forming a new strain of the virus. The current strain of swine flu has not been seen before in humans or in pigs.
"The virus changes in the pig lung and the pig nose, for example. And also in the human lung," said Gramer. "There are cells that bind up the viruses. If two viruses get into the same cell they can exchange the genetic material."
Those binding units are called peplomers. Under a microscope they appear to be fringy-phalanges, surrounding a virus. Those exchange with each other, helping to create a new virus.
One possibility investigators are looking into is whether an insect carrying avian flu infected a pig, where the virus mutated into something more like a swine flu, which is now mutating inside of humans.
"We're working with researchers around the world to see how this came about," said Gramer.
One thing's for sure: Gramer believes the name "swine flu" is not appropriate.
"We don't have any report of contact with sick pigs and we don't have reports of ill pigs associated with any of these outbreaks. It's an unfortunate name because there isn't any pig to human transmission and no evidence of this virus in pigs," she said.
When flu mutates and has part pig, part bird and part human flu, that doesn't necessarily mean it's going to be more difficult for humans to fight off.
"It could also make [the virus] weaker," said Gramer. "The virus could make a faulty change that makes it unfit, because it just isn't able to, what we call, proofread all its changes all the time."
"We don't have the predictive tools now to look at a virus in the laboratory and say 'Oh, it's got this combination, it's going to be worse,'" said Gramer.
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