Concerns raised over first line of flu defence Antiviral medication Tamiflu ineffective against other H1N1 virus

With the declaration of a worldwide swine flu pandemic near, serious questions are being raised about the effectiveness of Tamiflu, the drug that is widely considered the first line of defence against a deadly virus.

The WHO has raised its pandemic alert level to five, meaning a global outbreak is now imminent and mitigation measures must be finalized. But because an effective vaccine for the deadly swine flu that has claimed 160 lives is likely to take three to six months, the first line of defence would be antiviral drugs such as Tamiflu and Relenza.

Canada has stocked 50 million doses of antiviral drugs and Dr. David Butler-Jones, head of the Public Health Agency of Canada, says the country has sufficient stocks of Tamiflu "to treat those who require treatment up until when we get a vaccine."

Ottawa's chief medical officer of health, Dr. Isra Levy, says the drug will be a key part of the city's arsenal in a flu pandemic.

But recent laboratory tests, including some by the National Microbiology Laboratory, show that Tamiflu is not effective against the H1N1 virus that causes the common flu. These results raise a troubling question: If Tamiflu didn't work against the common Type A/H1N1 flu virus, will it be an effective against the new H1N1 virus that causes the Mexican variant of swine flu?

Some experts believe it may not and say the faith governments have placed in Tamiflu may be misplaced.

"National governments are placing multibillion orders for stockpiles of Roche's Tamiflu" but there is "no guarantee as yet that Tamiflu will prove effective against a pandemic strain," said a 2005 report by Informa Healthcare, a leading British-based pharmaceutical research, publishing and consulting group.

The doubts about Tamiflu were strengthened this flu season when tests showed that the drug was ineffective against most of the common flu viruses.

Canada's top lab in Winnipeg tested 225 A/H1N1 influenza "isolates" for Tamiflu resistance and all of them were resistant to the drug because of the virus's capacity to mutate. Tests in British Columbia also showed the A/H1N1 flu was resistant to Tamiflu. Tests in the U.S. have also come to similar conclusions.

Levy acknowledges that Tamiflu has not been effective this flu season and doctors have used alternative drugs to treat patients. But he says that doesn't necessarily mean the drug won't be effective against the "novel" flu virus.

"We've been cognizant that Tamiflu is not what the scientists have been recommending as the first line (of defence) for seasonal flu. We know from laboratory testing we've been doing over the last few months that many of the viruses we've been able to isolate for seasonal flu are resistant to Tamiflu," he said.

And that's why some people are saying, "Well, hang up a minute, the study says this virus is resistant to Tamiflu so why use it." Even more difficult for physicians in the treatment of patients is that when someone first shows up with symptoms, it's unclear immediately what flu strain they have.

But Levy says evidence gathered so far shows that the new flu is "susceptible" to Tamiflu.

"The fact that one H1N1 virus is resistant doesn't suggest a new H1N1 virus is going to be resistant," he said. "All the reports I've read so far coming out of the National Microbiology Laboratory is that the new flu is susceptible to Tamiflu."

What public health officials are worried about is not that Tamiflu will not work; rather, Levy says, overuse of the drug could compromise its effectiveness. Because flu viruses mutate rapidly, unnecessary use of Tamiflu could render it useless because the new virus could mutate and become resistant.

"If we overuse one of these agents (anti-viral drugs), if we use too much too quickly in the wrong situation, we run the risk of creating a situation where it will be resistant," he said. "And then six months down the road, when we get a worse situation, the agent would no longer be effective."

Dr. Brian Ward, associate director of the Research Institute at the McGill University Health Centre, said the common H1N1 flu virus and the new swine flu virus are "distant cousins" and there is little reason to believe that if one becomes resistant, the other one would also be. He agreed that the real danger of a drug like Tamiflu becoming ineffective is overuse.

"The only reason we should be worried is that one Canadian might be infected by both the seasonal and new flu virus, but that is remote," said Ward, an expert on viruses and vaccines.

Samantha Ouimet, spokeswoman for Roche Canada, the manufacturer of Tamiflu, said the drug did not work against the seasonal flu, but said the WHO and the U.S. Centers for Disease Control and Prevention have recommended its use against swine flu.

"There was resistance to Tamiflu this flu season, but both the WHO and the CDC say it is active against the new flu strain," Ouimet said.

In a statement, Roche said the company is working closely with the federal government to meet any additional need for Tamiflu. Roche said the company wants to meet the needs of public health before it considers commercial clients.

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5 -- World Health Organization Raises Pandemic Alert Level to ...

What it means: Human-to-human spread of the virus in at least two countries in one WHO region. Indicates that a pandemic is imminent.

What Level 6 means: A global pandemic is under way. This has not happened since 1968, when 'Hong Kong flu' killed about one million people.

19 -- Cases in Canada.

7 cases in Ontario.

0 suspected cases in Ottawa.

10 -- Countries With Confirmed Cases ...

Germany, Austria and PERU announced their first confirmed cases of swine flu on Wednesday, joining Mexico, the U.S., Canada, Spain, Britain, New Zealand and Israel.

16 other countries have suspected cases.

2,853 -- Suspected Cases Worldwide:

Confirmed cases: 184

What Should I Do to Protect Myself and Others

Treat the swine flu outbreak as you would any other flu season:

- Wash your hands often with soap and warm water

- Cover your mouth when you sneeze or cough; avoid touching eyes, nose, mouth

- Avoid close contact with those who are sick; stay home if you get ill