Researchers have created what they say is the first global map of malaria infection rates in more than 40 years, in an effort to help inform policy and monitor progress in fighting the disease.
The map of the extent of Plasmodium falciparum infection, the most deadly type of malaria parasite, is published today (24 March) in PLoS Medicine. It was produced by the Malaria Atlas Project (MAP), a multinational team of over 200 researchers.
The researchers used data from nearly 8,000 surveys of how many people were carrying the parasite in their bloodstream in malaria-prone areas in 2007 to map malaria risk.
They found that fewer people live in high-risk malaria areas than previously thought. Some 70 per cent of the 2.4 billion people in malaria-prone areas live in low-risk areas where mathematical models predict that simple interventions such as bednets could eradicate the disease.
"The map shows us, surprisingly, that the majority of the endemic world is in fact very low risk," says Bob Snow, one of the report's authors, from the Kenya Medical Research Institute and the UK-based University of Oxford.
All of Latin America was found to be at low risk, as was most of Central and South-East Asia, although pockets of intermediate and occasionally high transmission remain.
But the map also shows that the risk of contracting malaria remains high in Central and West Africa where control, rather than eradication, should therefore be the aim of the next ten years. Of the people estimated to live in high-risk areas worldwide, 98 per cent lived in Africa.
The map will be useful for policymakers, says Simon Hay of the University of Oxford, who led the project.
"We can now say exactly how many nets are needed in a country, where these should be distributed, where these are likely to be enough and where we must consider additional efforts like indoor residual spraying," he told SciDev.Net.
Richard Feachem, director of the Global Health Group at the University of California San Francisco, says the map will serve as encouragement to the 39 countries committed to eradicating the disease — all of which are identified by the map as low-risk.
But Richard Cibulskis, an epidemiologist at the WHO's Global Malaria Programme, says that while the map will be useful for global policymaking, it may be less suitable at a country level due to lack of data points, "making the map quite imprecise for some countries".
Another barrier to countries making use of the data is their limited capacity for data analysis and for monitoring control and eradication programmes, he adds.
The map and its data are available free online and will be updated annually. A similar mapping exercise is also planned for the malaria parasite Plasmodium vivax.
PLoS Medicine, doi 10.1371/journal.pmed.1000048 (2009)