Swine Flu Virus Hiding Out in Pigs, Gaining Strength

Farmer Fung Tang stands among her pigs in Hong Kong in August 2007.

Photograph by Paul Hilton, Bloomberg/Getty Images

Ker Than

Published June 17, 2010

The swine flu, or H1N1, virus has been hiding out in pigs for more than a year, getting a genetic makeover, scientists have discovered.

Pigs in a Hong Kong slaughterhouse are carrying influenza viruses containing gene segments belonging to the deadly H1N1 strain that swept the globe in 2009, tests reveal. (See swine myths and facts.)

The newly identified "reassorted" virus—dubbed 2010 H1N1—is likely not a threat to humans.

That's because only one of the virus' eight genetic segments belonged to the strain that infected humans last year, said study co-author Malik Peiris, an influenza researcher at Hong Kong University.

Swine Flu Could Hit Humans Again

The discovery is still disturbing, because it suggests the 2009 H1N1 virus could be reshaping its genetic code in animal hosts in other parts of the world. (Related: swine flu pictures.)

One of these emerging strains could come to resemble the 2009 H1N1 strain enough to make the jump back to humans again, Peiris said.

"I'm 100 percent certain that this is not unique to" Hong Kong, Peiris said.

That's why Peiris advocates increasing global surveillance of pigs to identify swine flu strains that could cross over to humans. (Read how scientists are tracking the next killer flu.)

"We're not saying this particular virus is a huge threat or that people should stop eating pork," he said, "but that this is likely happening in other places in the world. And there could be other combinations arising that could pose a threat to human health."

Research appears in this week's issue of the journal Science.