A new study published today in Nature (abstract here) suggests that there may have been as many as half a billion cases of Plasmodium falciparum across the world in 2002.
More than two-thirds of these occurred in Africa, where this more deadly form of malaria mostly affects children under-five. But far more cases than previously thought take place in SE Asia.
This is nearly twice the estimate of 273 million cases produced by the World Health Organisation (WHO) in 1998. In areas outside Africa, the new figures are at least three times as high as those previously estimated by the WHO.
The paper by Snow, Guerra, Norr, Myint and Hay emphasises that malaria treatment requires more investment for more people in more areas of the world than governments and health agencies might have anticipated.
The research used current 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. The research suggests that 2.2 billion people are at risk of malaria.
Professor Bob Snow said (press release):
"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.
Our work has demonstrated that nearly 25% of worldwide cases occur in South East Asia and the Western Pacific - whereas most people regard Plasmodium falciparum disease a problem particular to Africa.
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."