A spatial distribution map was published on February 25, 2008 in PLoS Medicine describing areas of risk for a deadly form of malaria. It indicates that more than 2.3 billion people (about 35 percent of the world’s population) live in areas that put them at risk for this disease.
Malaria is a disease that is caused by a protozoan parasite, most notably Plasmodium falciparum, that alternates its life cycle between the blood and the liver of its host. It generally occurs in tropical and subtropical regions of the world, where infected Anopheles mosquitoes bite humans and transmit the disease. 500 million cases of malaria are reported every year, and one million people die as a result of these infections. Most often, the victims are children living in sub-Saharan Africa.
When designing campaigns to control this disease, a good geographical picture of the areas of higher risks could be instrumental. This map was created by Robert W. Snow and colleagues at the Malaria Atlas Project (MAP), which is a collaboration between Kenyan Medical Research Institute and the University of Oxford, and is funded by the Wellcome Trust. They assembled information about malaria cases in thousands of communities in 87 different countries. Their sources included nationally reported data on cases of infection, travel advisories, and surveys in specific areas.
Other factors that affect the life cycle of the parasite, and thus the likelihood of active transmission, were also integrated — these especially include climatic conditions. For instance, when infected mosquitoes inhabit a climate with a particularly low temperature, infected mosquitoes have a short enough natural lifespan that the parasite does not mature to its infectious stage. This means that malaria transmission will not occur, and lowers the risk of transmission.
The resulting map shows the locations that have the highest risk of P. falciparum. Additionally, it provides an idea of what proportion of the population lives in areas of transmission where existing control strategies could theoretically eliminate the parasite. This study implies that this should be possible in more areas than was previously thought, and will help future malaria prevention efforts to focus further.
The resulting map is published online in an open access journal and available via their website, http://www.map.ox.ac.uk, to be updated as new data become available. In doing this, the authors intend to guarantee universal availability and expedite further updates.
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The Limits and Intensity of Plasmodium falciparum Transmission: Implications for Malaria Control and Elimination Worldwide
Carlos A. Guerra, Priscilla W. Gikandi, Andrew J. Tatem, Abdisalan M. Noor, Dave L. Smith, Simon I. Hay, Robert W. Snow
PLoS Med 5(2): e38
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Written by Anna Sophia McKenney