Expect to see more cases of humans transmitting the H1N1 flu strain to pigs, but that should not be cause for concern as swine are not severely affected by the virus, according to the World Organization for Animal Health (known as OIE).

On May 2, Canadian health officials reported that a swine herd in Alberta had caught the virus from a carpenter who had recently returned from Mexico, the suspected center of the flu outbreak that has spread to 46 nations.

“It is the only reported case of the virus being transmitted from a human to a pig in the world. We would not be surprised if we have other cases like this in other countries,” says OIE Director General Bernard Vallat.

“But it is not a problem because we know pigs are not a big player in the epidemiological spread of the disease,” he adds.

Vallat reiterates that flu viruses are known to easily circulate between species, especially when strains are mixed. The novel H1N1 virus features human, bird and pig components.

Pigs have long been considered a potential source for new and novel influenza viruses that infect humans, according to the U.S. Department of Agriculture’s Agricultural Research Service (ARS). Pigs have receptors on their cells that bind mammalian and avian influenza viruses, multiplying the odds that there will be an exchange of genetic segments o the virus.

ARS researchers tested serum samples from pigs previously infected with swine influenza virus (SIV) or vaccinated with commercial vaccines to determine if U.S. swine herds are susceptible to the new H1N1 influenza virus. Results suggest that previous immunity to swine flu may not protect pigs from the H1N1 flu virus currently circulating in people.

Also, importantly, current swine flu vaccines may not be effective against the new H1N1 flu virus.

The next step for ARS scientists is to test the efficacy of SIV vaccines in a pig vaccination challenge to find out if antibodies in vaccinated pigs correlate with protection against the new virus.