New risk maps identify geographic areas predicting spread of avian flu

The 2003 epidemic of Highly Pathogenic Avian Influenza (HPAI) in the Netherlands is the only recent epidemic of HPAI in the developed world.

Gert-Jan Boender and colleagues have examined the data from this outbreak and produced a model which can predict the probability of infection from one farm to another; the 'transmission kernel'. They also identify high-risk areas in the Netherlands and analyze various control strategies, concluding that in these regions an epidemic can only be brought to an end by massive culling of susceptible farms.

For avian influenza, the analyses show that there are two poultry-dense areas in The Netherlands where epidemic spread is possible, one in the central region and one in the south, close to the German and Belgian border. The authors suggest local control measures are unlikely to be able to halt an unfolding epidemic in these areas.

The paper, published in the Open Access journal PLoS Computational Biology, arrives at these conclusions through a computational (or mathematical) modeling method, an approach which has already proved its worth in the analysis of infectious diseases such as the 2001 foot-and-mouth outbreak in the UK. The method can estimate the key parameters which determine the spread of highly transmissible animal diseases between farms. These risk maps identify geographic areas in which a given intervention strategy fails to control the spread of the disease between farms. "The risk map concept is an instrument suitable for analyses of epidemic control options both during crisis and in peacetime" says Boender.

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