Pig are potential mixing vessels for new strains of swine flu. (CBC)

Human and animal influenza experts tried to minimize fears on Monday that a herd of pigs in Alberta infected by swine flu could potentially make the infection more dangerous to humans.

Usually viruses move around within a single species, but scientists say pigs are different because their lungs have receptors that make them susceptible to swine, human and avian influenza viruses.

It's not a surprise that a farm worker in Alberta with the H1N1 virus was able to pass it along to pigs, but it is a concern when infections spread across species, said Earl Brown, a virologist at the University of Ottawa.

"It's possible that you're going to get more change and you don't know if change is good or bad," Brown said. "So it maybe speaks to a little less stability."

The pigs' susceptibility to bird and human influenza viruses make them potential mixing vessels to breed new strains. If the pigs infected in Alberta had another virus when they contracted the new H1N1 avian influenza, such as the common seasonal pig flu H3N2, the two viruses could share genetic material to produce a mutated virus — a process called reassortment.

The odds of reassortment happening now in Alberta are slim, said John Harding, a swine health specialist at the University of Saskatchewan's Large Animal Clinical Sciences.

"The chances of this H1N1 virus infecting a pig at the same time it's infected with another virus I think is very, very rare simply because we just don't see that many pig influenza viruses occurring this time of year," Harding said.

There are flu seasons in pigs like in people, and influenza illness is short-lived in swine. The pigs in Alberta are already recovering.

Surveillance urged on farms

If two viral strains defied the odds and combined, it wouldn't necessarily be a more virulent strain. It also wouldn't necessarily be able to infect people, since the genes responsible for transmission to people could be lost in the reassortment process, Harding said.

Regardless, people who work with pigs should stay away from farms if they have flu symptoms, he advised. The Canadian Food Inspection Agency has also asked producers and veterinarians to increase their biosafety measures to limit any risks to animal health.

Farming operations should be vigilant about surveillance and containment since animals could end up putting a strain on the human health system, said Brown.

As flu season for pigs and people wraps up in North America and Europe, it is just beginning in the southern hemisphere.