There have been five documented cases of Tamiflu-resistant swine flu worldwide. (Michael Probst/Associated Press)

Health officials say a recent Quebec case of drug-resistant swine flu shouldn't prompt Canada to change its approach to Tamiflu, as the strain remains rare worldwide.

A 60-year-old Quebec man is one of five people around the world found to have a strain of H1N1 flu resistant to the antiviral drug Tamiflu (oseltamivir). The other cases occurred in Japan, Denmark and Hong Kong.

The Quebecer was given a low preventive dose of Tamiflu as a precaution because he had a pulmonary condition and doctors thought he might have been exposed to swine flu.

Experts are debating whether Tamiflu should be given to prevent people from getting sick or whether doctors should wait until symptoms appear before prescribing it. Currently, the Public Health Agency of Canada only recommends using Tamiflu for treatment after symptoms emerge, to help stave off the development of resistance to the drug.

However, Dr. Guy Boivin, Canada Research Chair on emerging viruses and antiviral resistance in Quebec City, said he suspected the man was already infected with H1N1 virus when he was given the Tamiflu.

There is no evidence the man transmitted the resistant virus to anyone else, Boivin said. He recovered and was never hospitalized.

Treat symptoms quickly

"In some cases, it's probably better to wait until we have the symptoms," said Boivin, who works at the Infectious Disease Research Centre in Quebec City. "But rapidly after symptom onset, treat with high doses of the anti-viral drug."

There are few cases of resistance worldwide, which means Canada's approach to swine flu should stay the same, Boivin said.

Health officials are watching for signs that the resistant strain might spread person to person or become more or less dangerous.

"Just because he ended up with a drug-resistant strain doesn't necessarily mean that that strain has the 'right stuff' to be able to go person to person to person," said Dr. Michael Gardam of the Ontario Agency for Health Protection and Promotion.

"Usually when you see Tamiflu-resistant strains, they actually aren't very good at spreading person to person. That isn't always the case. There is one strain that's out there that's very good at spreading person to person. But right now, we don't have any evidence that this strain is one of those strains that is able to do that."

Gardam said he and other health officials are watching closely for clusters of Tamiflu-resistant cases among people who hadn't been on the drug, which would indicate the resistant strain is starting to move from person to person.

Health officials also continue to take swabs of people sick enough to go to emergency to check for any mutations in the virus. Anyone who is sick enough to go to emergency should be treated with Tamiflu, Gardam said, adding the drug works best if given with the first 48 hours after showing symptoms.

Stockpile still works

About 80 per cent of Canada's stockpile of antiviral medications consists of 50 million doses of Tamiflu, which remains effective. Boivin said he would like to see companies develop alternative antivirals in case more drug resistance occurs.

The other 20 per cent of Canada's stockpile is the antiviral drug Relenza (zanamivir), which is harder to administer than Tamiflu because it has to be inhaled into the lungs, Gardam said.

The company that manufactures Tamiflu, Roche, said its research shows a small percentage of people will not respond to the drug.

"We know that there are various reasons for the resistance. What we know is that it's not drug-induced, that it's some kind of natural mutation," said Laura Pagnotta, who speaks for Roche Canada.

Pagnotta said the World Health Organization still recommends Tamiflu for the prevention and treatment of swine flu, but says it should be prescribed on a case-by-case basis.

Health officials continue to recommend that people:

• Wash their hands often with warm, soapy water or hand sanitizer.
• Cough and sneeze into your arm, not your hand.
• Keep common surfaces and items clean and disinfected.
• Stay home if you're sick, unless directed to seek medical care.

The worldwide death toll from swine flu is more than 700, according to the World Health Organization, which recently stopped counting the number of cases worldwide.

As of last week, Canada was reporting more than 10,000 swine flu cases, with 45 deaths. Between 4,000 and 8,000 Canadians die of influenza and its complications annually, depending on the severity of the season, the Public Health Agency said.

With files from The Canadian Press