TORONTO (CP) - A flu pandemic could be extinguished at its source with a rapid response combining antiviral drugs, quarantine and perhaps vaccination, two international groups of mathematical modellers reported Wednesday in prominent scientific journals.

The notion is likely to provoke sustained and heated debate over the merits and disadvantages of attempting what has always been thought to be an unattainable goal - halting the spread of an emerging pandemic virus before it sickens and kills millions around the globe.

Dr. Margaret Chan, the World Health Organization's new representative for pandemic influenza, called the idea "an attractive theory."

But she wondered whether countries likely to be at the epicentre of a new pandemic would be able to rapidly detect, diagnose and report human cases of H5N1 avian flu - believed to be the top pandemic threat at present - in time to translate computer-generated predictions into real-life results.

"There is no doubt a window of opportunity," Chan said in an interview from Geneva. "However, the situations on the ground may narrow that opportunity further."

Chan said it was too soon to say whether it made sense for the WHO to try to lead an effort to implement the plans laid out in the models.

But she did admit the Geneva-based organization is in discussions with the Swiss drug giant, Roche, to increase its stockpile of the antiviral oseltamivir, the key drug in any containment effort.

A spokesperson for Roche, which earlier gave the WHO 120,000 treatment courses of the drug, said the company is in the final stages of talks to provide "a significant amount more Tamiflu," the drug's brand name.

"We're donating drug," said Paul Brown, former head of the Tamiflu global team and now a vice-president at Roche Canada.

The scientists who led the studies said there are no guarantees their plans would work. But given the huge human and economic tolls a pandemic might exact, they said the remarkably similar and positive outcomes of their modelling work make it incumbent on the world community to try.

"I do think we have a moral obligation to try to stop pandemic flu at the source," insisted Ira Longini, a mathematical modeller from Emory University in Atlanta and lead author of one of the studies, which appears in this week's issue of the journal Science.

"There are many, many uncertainties and many reasons why you could be skeptical . . . about the possibility of containment working and being feasible," acknowledged Neil Ferguson, lead author of the other paper - published in Nature - and a professor of mathematical biology at Imperial College in London, England.

"(But) the fact that it can give such large benefits - potentially saving millions of lives because you stop a pandemic in its tracks - makes me argue that really, significant commitment should be made to at least trying to make it work." 

The models suggested that with relatively modest stockpiles of drug - Longini estimated 100,000 to one million treatment courses; Ferguson said it would take up to three million - and quarantining of cases and contacts, a new flu strain that was spreading among humans could be tamped out.

In both models success is predicated on many factors that are not givens. The drug would have to work on the emerging virus. Cases would have to be found and treated quickly. A high percentage of case contacts would have to be placed on the drug rapidly to keep them from getting sick and would have to be quarantined. As well, containment would only work if the virus is not too infectious at the start.

Other important caveats include a single outbreak as opposed to multiple simultaneous outbreaks in diverse geographic locations, and a start in a rural setting.

Both modellers admit there would be little or no chance of extinguishing a pandemic if it started in a large Asian city. "Somebody would get on a plane. The urban areas are too connected to the rest of the world," Longini said.

While the idea of stopping a pandemic has universal appeal, many - including Canada's Health Minister Ujjal Dosanjh - wonder whether the idea is plausible at present.

"I think experts would agree that at this time, we might not have the collective capacity internationally to quickly detect the emergence of pandemic early enough to make a difference," he said from Victoria.

A leading advocate for global pandemic preparedness said the models don't take into account the state of public health infrastructure in Southeast Asia, illustrating the frailty of the systems by comparing an emerging pandemic to a fire. In the analogy, antiviral drugs are water.

"You don't have trained firemen, you don't have a fire truck, you don't have hose, you don't have a nozzle, then I don't think the water's worth much," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

"I'm willing to support that approach - providing antivirals - but it's only if you have the whole complete package.

"If you don't have surveillance, you don't have diagnostic (tests), you don't have ability to bring some kind of population movement control into play and you don't have surveillance in adjoining areas (countries), I don't think that this is going to have any real impact."

Other modellers suggested the number of lucky breaks the world would need puts in some doubt the chances of success.

"I think that by their own descriptions, many things that are uncertain have to fall in one direction, mainly the more optimistic direction, for this to work," said Marc Lipsitch, a professor of epidemiology, immunology and infectious diseases at Harvard University's School of Public Health.

But Dr. Scott Dowell, former director of the U.S. Centers for Disease Control's international emerging infections program (based in Thailand), argued the modelling studies provide an opportunity to foster significant improvements in disease surveillance and response capacities in Southeast Asia.