The anti-viral drug Tamilfu is used to treat people infected with swine flu. (Michael Probst/Canadian Press)

The Vancouver Island health authority is advising people with chronic medical conditions like asthma and diabetes to get a prescription for an antiviral medication before they get sick with swine flu.

Dr. Richard Stanwick, medical officer for southern Vancouver Island, says taking the antiviral drug Tamiflu won't prevent people from getting the H1N1 virus.

But taking it within 12 hours of catching swine flu could mean the difference between life and death for people with health conditions that give them a higher risk of respiratory failure.

"This is an opportunity to intervene early in the course of the infection and we implore people who are in these risk groups to take the opportunity to take what steps they can until a vaccine is available," said Stanwick.

"If you have asthma, if you are on cancer treatment, if you've got lupus — I mean there is a whole long list of diseases that people need to be aware of — contracting the virus puts you at increased risk of the complications, and that's why we have to use Tamiflu to intervene," he said.

Children are also at increased risk of becoming seriously ill from swine flu, Stanwick said.

No vaccine yet

There is enough Tamiflu available for those at risk in B.C., but a vaccine to prevent swine flu will not be available until November, he said.

Isolated cases of drug-resistant swine flu have being reported around the world, including one case in Alberta this month and another in Quebec in July.

The advice comes after outbreaks of the virus were reported in several communities on Vancouver Island.

Health officials say that so far this year six people in B.C. have died after contracting the virus, but all had other health conditions. Roughly 50 people with the virus have been treated in hospital.