TORONTO - Canada has recorded a case of Tamiflu-resistant swine flu virus, in a Quebec man who had been given the drug to prevent infection.

The case is the fourth reported globally since the new H1N1 virus was discovered in April.

The man, 60, was given the flu antiviral after his son fell ill with the pandemic virus. It's believed the resistance arose in the man and there is no evidence he transmitted resistant virus to anyone else.

"It appears to be an isolated case," said Jirina Vlk, spokesperson for the Public Health Agency of Canada.

"Although the strain does not appear to have spread beyond the reported individual case we continue to be vigilant on this front."

Use of Tamiflu to prevent infection - a procedure called prophylaxis - has been seen on occasion to give rise to resistant viruses.

"We know that it was going to happen and it's not good news that it's happening," said Dr. Allison McGeer, an influenza expert at Toronto's Mount Sinai University.

But she said given the amount of Tamiflu being used in the world right now, such cases are bound to arise.

"It's the problem with influenza, right? Either we're going to see small numbers of these and they're just going to kind of appear periodically and we're all going to worry or it's going to go big," McGeer said.

"There's probably not going to be much in between."

This is the fourth case reported so far of Tamiflu resistance in swine flu cases; earlier cases were reported from Denmark, Japan and Hong Kong. Three of the four cases arose in people who had been taking the drug.

The other was in a girl from San Francisco who travelled to Hong Kong and was discovered to be ill there. She hadn't taken the drug, suggesting the virus that caused her infection was already resistant. U.S. officials have intensified surveillance for resistant viruses in the San Francisco area but say they have not found other cases.

The Public Health Agency says the man recovered from his bout of swine flu without complications and never needed hospitalization.

Vlk said the agency recommends using Tamiflu for treatment only, adding prudent use of the drug could stave off the development of resistance.

-Follow Canadian Press Medical Writer Helen Branswell's flu updates on Twitter at CP-Branswell

Most Popular From ...