Preventing A Global Pandemic of Avian Flu is Feasible

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Avian Flu

A global pandemic of avian flu costing millions of lives could be prevented if governments immediately take the right steps to contain it, scientists report today in Nature.

Using a computer model, researchers simulated an outbreak in rural Thailand of a H5N1 influenza virus mutated to become transmissible from person to person. Currently H5N1 is transmitted to from birds to people and person-to-person transmission is very rare. However the virus is so lethal that if it were to become more transmissible, the consequences of a global pandemic could be disastrous.

After simulating a large number of policy options, researchers found the best containment strategy combined antiviral drugs given to people in the same school, workplace or geographic area as those infected and reduction of travel in and out of affected areas.

To bring an outbreak quickly under control, limiting its size to fewer than 200 cases, two key conditions need to be met, according to the model. The virus would need to be identified whilst infection was confined to around 30 people and courses of antiviral drugs would need to be given rapidly to the 20,000 individuals nearest those infected.

Containing the spread of the virus is increasingly difficult once more than 40 cases have occurred or the outbreak has reached major cities. This is due to the larger numbers of people needing treatment and the rising likelihood that infection will spread internationally before it is brought under control.

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Professor Neil Ferguson, from Imperial College London, lead researcher on the study alongside colleagues from institutions in the US, France, Hong Kong and Thailand, said: "Stopping an emergent pandemic in its tracks at an early stage is the only strategy which could have a dramatic impact on the levels of death and disease that a new pandemic would cause."

"Containment is challenging. We can't just cherry-pick the more easily implemented options, such as closing schools and encouraging people to stay home, and expect to have a containment strategy with a good chance of success against a moderately transmissible pandemic virus," added Professor Ferguson.

Administering antiviral drugs to the entire population of a country in the event of an outbreak would require millions of doses, making this an unfeasible option. However, an international stockpile of 3 million courses of the drug would be sufficient to contain an outbreak, if it could be deployed anywhere in the world at short notice and if the outbreak was caught in time, say the authors.

The researchers argue that all countries should contribute to ensuring that the appropriate resources and infrastructure are in place in East Asia and Southern China, the regions where an outbreak is most likely to start. The simulation focused on Thailand but the researchers believe that their general conclusions would be valid across these regions.

"It is vital that the international community prepares now to ensure that containment is given the best possible chance of success, because the costs of failure are potentially so catastrophic. The joint commitment of countries in South East Asia and of international agencies is needed to overcome the challenges to making containment a feasible policy across the region," added Professor Ferguson.

The research was sponsored by the U.S. National Institutes of Health MIDAS program. Professor Ferguson is a Howard Hughes Medical Institute scholar.

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