Researchers have long known that pigs are a living breathing incubator for influenza because they have receptors for human, swine and even avian versions of the virus.
"So what appears to have happened in the mixing, it's now acquired genetic material allowing it to transmit person to person," Dr. Lawrence Drew said.
Drew is the director of clinical virology at the University of California, San Francisco. He believes this current outbreak could turn out to be mild, because North Americans have been exposed to the human version of the H1N1 flu virus, dating back to the terrible Spanish flu epidemic.
But what if another animal virus were to accomplish the same kind of human to human mutation?
"If that can occur with the swine virus, can it also occur with the bird flu virus," Drew said.
The bird flu virus, known as H5N1, erupted a decade ago in Asia. North Americans have had little or no exposure. So far, it has not shown the ability to spread human to human.
"If it gets that ability, being a totally new virus none of us have seen before, makes it become the leading candidate to become a pandemic," Drew said.
Experts like Dr. Charles Chiu at CUSF's virology lab say researchers will now race to assemble the genetic sequence of the new swine flu virus.
"The technology has advanced to the stage where we could feasibly sequence the entire genomes of the influenza viruses, or this particular strain, in single step," Chiu said.
That, he says, could tell them more about its origins, how it mutated and possibly provide a model for future outbreaks.
"If avian influenza does become a pandemic strain, does become capable of human to human transmission, it's very likely it will arrive through a similar pathway," Chiu said.
Chiu says studying the mutation pattern of this virus could also help researchers predict whether future strains will develop resistance to current flu drugs, and which strategies would work best in fighting those new strains.