New Estimates on Extent of Malaria

A new comprehensive investigation into the extent of the deadliest form of malaria shows there were over half a billion cases in 2002. More than two-thirds of these occurred in Africa, where Plasmodium falciparum malaria mostly affects children under five. But far more cases than previously thought take place in Southeast Asia.

The latest estimate of 515 million episodes is described in todays edition of Nature and emphasizes that malaria treatment requires more investment for more people in more areas of the world than governments and health agencies might have anticipated.

This research is timely because the United Nations has set up initiatives targeting malaria. The Millennium Development Goal aims to halt the spread of the disease by 2015 and Roll Back Malaria is designed to halve mortality in the next six years.

Scientists from the University of Oxford, based at the Kenya Medical Research Institute -- Wellcome Trust Research Program used contemporary and historical epidemiological, geographical and demographic information to model where people live, the likelihood of infection from malaria parasites and susceptibility to developing the disease. New methods in Geographic Information Systems and data from earth orbiting satellites were used.

We have taken a conservative approach to estimating how many attacks occur globally each year, but even so, the problem is far bigger than we previously thought, says Professor Bob Snow, who led the research, which suggests 2.2 billion people are at risk from malaria.

We have taken a science-driven approach to working out who is at risk, where they are located and what their chances would be of developing an attack of malaria, Snow continues. Our work has demonstrated that nearly 25 percent of worldwide cases occur in Southeast Asia and the western Pacific, whereas most people regard Plasmodium falciparum disease a problem particular to Africa.

Getting numbers right is important. Not knowing the size of the problem limits our ability to articulate how much money we need to tackle the problem - not knowing where the problem is located means you cant spend wisely.

This is particularly important for new drugs needed to fight malaria. These are expensive and difficult to produce, and production capacity and financing can be driven by speculation, poor data or simply best guesses. We need to do a better job -- driven by data -- on working out the burden posed by this killer parasite if we are serious about international goals and targets set by development partners.

World leaders are now seriously focusing on malaria as a problem that can be tackled with tools we know work and are comparatively cheap. Hopefully these data will provide not only more ammunition as to why they should take it seriously but help them decide where to spend their money to best effect.

If we are going to roll back malaria then we need to know the size of the problem, and where it is, says international malaria expert Professor Nick White, director of the Wellcome Trusts Southeast Asia unit. Falciparum malaria has increasingly been thought of as an African problem. These estimates challenge that notion and suggest there is a lot more falciparum malaria in Southeast Asia than previously thought.

The work by Snow and his colleagues is important, says Dr. Richard Feachem, executive director of the Global Fund to Fight AIDS Tuberculosis and Malaria. Many have believed that existing data grossly underestimates malaria, morbidity and mortality in Africa and Asia. We now have confirmation of this.

Accurate numbers are essential to the Global Fund, which is charged by the international community with financing the counter-attack against malaria, especially through purchases of effective drugs and insecticide-treated bednets. We must now significantly increase our estimates of resources needed.

Source: Wellcome Trust