Using a small stockpile of a secondary antiviral drug in a flu pandemic

Apr 30, 2009

In a global influenza pandemic, small stockpiles of a secondary flu medication - if used early in local outbreaks - could extend the effectiveness of primary drug stockpiles, according to research made available today ahead of publication in PLoS Medicine.

Many countries are investing in large stockpiles of a single drug, oseltamivir (). But influenza viruses can become resistant to , and the widespread use of a single drug is likely to increase the risk that a resistant strain will emerge. If such a strain were to spread widely, the effectiveness of antiviral drugs in treating infected patients, as well as their ability to slow the spread of a pandemic, would be greatly reduced.

This video is not supported by your browser at this time.

Using a to represent the global spread of pandemic influenza, an international team of researchers led by Joseph Wu of the University of Hong Kong, and including collaborators in the UK and the US, found that treating as few as only the first 1% of the population in a local with a secondary drug rather than with oseltamivir, could substantially delay the development of resistance to oseltamivir. This reduction in resistance was predicted to benefit not only local populations, but also those in distant parts of the world where the pandemic would subsequently spread through air travel.

In the context of the currently emerging swine flu, the secondary drug could be zanamivir (Relenza), the only other approved drug to which the new H1N1 strain has been found to be susceptible.

This strategy is predicted to be effective because it delays use of the primary stockpiled drug until a certain proportion of the local population (about 1.5% according to the model) has been infected with virus that remains susceptible to the primary drug. With drug-sensitive virus in the majority as people recover from infection and develop immunity, only a minority of further infections are likely to be resistant to the primary drug.

Technically, such a delay could be achieved by postponing the launch of any antiviral intervention. However, because even a short delay would mean denying antiviral drugs to people who would benefit from them, the researchers instead propose the deployment of a small stockpile of a secondary antiviral during the early phase of the local epidemic.

The model, prepared before the current swine flu crisis, considered two possible strategies, "early combination chemotherapy" (treatment with two drugs together while both are available, assuming that clinical trials show such a combination to be safe for patients) and "sequential multi-drug chemotherapy" (treatment with the secondary drug until its stockpile is exhausted, then treatment with the primary drug). While either strategy could be effective in principle, only the sequential strategy would be practical in responding to the currently emerging H1N1 , because the safety of combining zanamivir with oseltamivir (for combination therapy) is not established.

After simulating the impact of these strategies in a single population, the researchers then introduced international travel data into their model to investigate whether these two strategies could limit the development of antiviral resistance at a global scale. This analysis predicted that, provided the population that was the main source of resistant strains used one of the strategies, both strategies in distant, subsequently affected populations would be able to reduce the consequences of resistance, even if some intermediate populations failed to control resistance.

Source: Public Library of Science (news : web)

Explore further: Bacteria blamed in indigenous Mexican baby deaths

Related Stories

Major flu strain resistant to widely used antiviral drug

Jan 15, 2009

One of the major strains of the influenza virus this season has become resistant to Tamiflu - rendering the mainstay antiviral drug all but impotent and creating tough treatment options for patients who come down with the ...

Recommended for you

MSF fighting cholera outbreak in Tanzania refugee camps

14 hours ago

Medical charity Medecins sans Frontieres (MSF, Doctors Without Borders) said Sunday it had launched emergency treatment centres in Tanzania, where thousands of Burundians fleeing unrest have been hit by cholera.

Bacteria blamed in indigenous Mexican baby deaths

May 23, 2015

Bacteria—and not a contaminated vaccine as initially suspected—were to blame for the recent deaths of two Mexican babies and for sickening 29 others, according to an official investigation.

Explainer: What is Chagas disease?

May 22, 2015

According to an article in the Journal of the American Medical Association (JAMA), in a Los Angeles clinic treating patients with heart failure, about 20% of Latin American patients have Chagas disease. What is that?, y ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.