Politics and pandemic planningDec. 8, 2005. 01:00 AMJEREMY...

Politics and pandemic planning

Dec. 8, 2005. 01:00 AM

JEREMY CARVER AND WANDA BUCHANAN

With the election campaign well underway, there is an important issue noticeably absent: What do our leaders propose for Canadians to better prepare against the threat of an influenza pandemic?

Such a pandemic will impact on everything from health care to immigration and trade, to the daily operations of business and government. Yet we have not heard one sentence related to pandemic strategy from any candidate.

Still, in the space of a few months many other governments around the world have stepped up preparedness planning, modifying their strategies to include stockpiles of a second anti-influenza drug, Relenza. While Canada has yet to announce its intent to do so, all governments — including our own — need to go even further, to include the development of new anti-virals.

This is our best chance for effective containment against a flu pandemic. That's why scientific experts from 15 countries are poised to start work for the Canadian-led International Consortium on Anti-Virals (ICAV). Collaborations with the Pasteur Institute in Paris, Oxford University in the U.K., Griffiths University in Australia and many other institutions have resulted in six lead compounds already identified for development.

ICAV has been working with the federal government and continues to work with provincial governments to find the $70 million required for the Canadian component. ICAV is also working with its colleagues from other countries to stimulate their governments to join in. France and Australia are actively engaged.

We need to hear more from federal candidates about what they will do to ensure Canada maintains its efforts to combat a viral pandemic, especially in light of the global health ministers' meeting held in Ottawa this past fall.

Viruses are constantly evolving, or mutating, in response to changes in their environment. Massive exposure to an anti-viral drug exerts pressure on this process and results in viruses that are resistant to the drug. So one drug can contain a virus for only so long. Sooner or later, resistant forms will emerge, not only to the first drug used but to the second and the third — and so on.

Nature recently reported the results of a careful analysis of a virus sample obtained from a young woman in Vietnam, infected with H5N1 even though she was taking the anti-viral Tamiflu as a protective measure. The mixture of H5N1 viruses isolated from this patient, when tested for sensitivity to Tamiflu, was found to be less susceptible (about 150-fold) than a sample taken from her brother, who had been infected earlier. The reason why her sample was less susceptible was that it contained a mixture of both sensitive and highly resistant viruses. The assay measured the average behaviour of the sample. When the highly resistant virus was cloned out of the mixture, it was found to be more than 1,000 times more resistant to Tamiflu than the sensitive form. It also contained a mutation well known in the laboratory to cause such extreme resistance. This is typical virus behaviour. H5N1 is behaving no differently than other human influenza viruses, such as H3N2 where, in a clinical study, 18 per cent of children treated with Tamiflu were found to develop resistant forms of the human influenza virus after treatment.

A flu pandemic will not be triggered by an identified H5N1-infected patient who has been treated with Tamiflu. It may, however, be triggered by an undetected patient who has been infected with an H5N1 strain that has acquired the ability to spread efficiently from human to human. Such was the case with the Spanish Flu in 1918 — now known to be an avian flu virus that, through mutation, jumped from birds to humans.

Once H5N1 gains the ability to transmit efficiently between humans, Tamiflu will be widely used to try to contain the outbreak and to prevent it from becoming a pandemic. The widespread use of Tamiflu will result inevitably in the emergence of a resistant form of H5N1. With Relenza added to the stockpile, we stand a better chance to contain the outbreak. Moreover, knowing the typical behaviour of viruses, it is only logical that we look beyond Relenza to the next stage. Our experience with HIV has shown us that containment of a highly pathogenic virus requires many drugs in the arsenal.

It is clear that world governments are beginning to look at the importance of having a variety of anti-virals as part of a multi-pronged pandemic response. While there is no doubt that universally accessible, effective vaccines are the long-term solution, we have to make it to the long term. Funding for anti-viral research and development is the key to getting us there — while we still have time.

Ask your local candidates what they would do, if elected, to better prepare Canadians against the threat of pandemic influenza — it may be they have an answer we'd all like to hear.

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