Tuesday, August 10, 2010

Population at risk

Nearly 3 billion people live at risk of infection with Plasmodium vivax, one of the most common varieties of the blood-borne malaria parasite. A global distribution map, "published August 3 in the open-access journal PLoS Neglected Tropical Diseases," estimates that 2.85 billion people live in areas and conditions that put them at risk for contracting deadly malaria.

Malaria is a parasite that infects humans and is transmitted through the bite of an anopheles mosquito. Every year 250-500 million cases of malaria are reported, many malaria cases end in death. In recent years, scientists, doctors, and health-care workers have made progress against malaria. Still, more information is needed to truly understand how effective treatments and preventative techniques are against malaria and where these techniques still need to be applied.

"The map, created as part of the Malaria Atlas Project (MAP), a multinational research collaboration funded mainly by the Wellcome Trust, reviews a host of information that challenges the dogma that P. vivax transmission is absent through large swathes of Africa and uses novel methods...to estimate global populations at risk."

Of the nearly "3 billion people exposed to some risk of P. vivax" malaria transmission in 2009, 91% live in Central and South East Asia. It is important to note that "more than half of those exposed to this risk live in areas where P. vivax malaria transmission is extremely low or unstable". In these areas, prospects of sustained malaria control and "elimination are relatively good".

The authors of this study used the most recently available P. vivax data from reported cases for all malaria-endemic countries and classified risk into three classes: malaria free, unstable, and stable. Risk areas were further refined, and some regions were eliminated based on temperature, aridity, and isolation. Some urban regions known to be malaria-free were also excluded from the at-risk population estimate.

"This study represents the first step in our efforts to provide the malaria control and research community with an evidence-based cartography of P. vivax malaria," says co-author Dr. Simon Hay of the University of Oxford. "We can now focus on trying to model the endemicity of the disease to provide more detailed global burden estimates, although this is complicated by the unusual biology of P. vivax."

Co-author Dr Carlos Guerra adds: "New evidence shows that P. vivax malaria is not as benign as was thought, and yet, as our study shows, remains the most widespread form of human malaria. Understanding where transmission of this parasite occurs at the global scale is fundamental in planning strategies for the control of this debilitating, and often lethal, disease."

Further information about the Malaria Atlas Project can be found at www.map.ox.ac.uk.

Guerra CA, Howes RE, Patil AP, Gething PW, Van Boeckel TP, et al. The International Limits and Population at Risk of Plasmodium vivax Transmission in 2009. PLoS Neglected Tropical Diseases, 2010; 4 (8): e774 DOI: 10.1371/journal.pntd.0000774

Malaria Atlas Project [MAP]. www.map.ox.ac.uk. Retrieved August 10, 2010.

Public Library of Science (2010, August 4). New estimates of the global population at risk of Plasmodium vivax malaria. ScienceDaily. Retrieved August 10, 2010, from http://www.sciencedaily.com­ /releases/2010/08/100803174854.htm

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