Preventing a global pandemic of avian flu is feasible if measures taken in time, says new research

Under embargo for
18.00 BST
Wednesday 3 August 2005

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.

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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A press briefing on this study is being held at 10am on Wednesday 3 August at the Science Media Centre, 21 Albemarle Street, London W1S 4BS (under embargo until 18.00 BST).
The speakers are: Neil Ferguson, Imperial College London; Peter Aldhous, Nature; and Ira Longini, Emory University. If you would like to attend please email Becky Morelle bmorelle@ri.ac.uk

For further information:

Laura Gallagher
Press Officer
Communications Division
Imperial College London
Tel: +44 (0)20 7594 6702
Mobile: +44 (0)7803 886248
E-mail: press.office@imperial.ac.uk

Notes to editors:

1. Strategies for containing an emerging influenza pandemic in SE Asia Advance Online Publication, 3 August 2005. DOI 10.1038/nature04017

2. Neil M. Ferguson1, Derek Cummings2, Simon Cauchemez3, Christophe Fraser1, Steven Riley4, Aronrag Meeyai1, Sopon Iamsirithaworn5 and Donald Burke2

1Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK

2Department of International Health, John Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland, 21205, USA

3INSERM U707, 27 Rue Chaligny, Paris, 75571 cedex 12, France

4Department of Community Medicine, 5/F William M.W. Mong Block, Faculty of Medicine Building, 21 Sassoon Road, Hong Kong

5Bureau of Epidemiology, Department of Diseases Control, Ministry of Public Health, Tivanonda Road, Nonthaburi 11000, Thailand

3. Consistently rated in the top three UK university institutions, Imperial College London is a world leading science-based university whose reputation for excellence in teaching and research attracts students (11,000) and staff (6,000) of the highest international quality.
Innovative research at the College explores the interface between science, medicine, engineering and management and delivers practical solutions that enhance the quality of life and the environment - underpinned by a dynamic enterprise culture.
Website: www.imperial.ac.uk

4. The U.S. National Institutes of Health MIDAS program is a research network that develops computational models of disease spread to aid the development of effective control strategies. More information about MIDAS is available at www.nigms.nih.gov/research/midas/index.html