Number of Cases of Deadliest Form of Malaria Could Be Twice as High as Previous WHO Estimates, Study Says

The number of cases of the "deadliest" strain of malaria could be up to twice as high as previous World Health Organization estimates, potentially making the disease more lethal than HIV/AIDS, according to a study published in the March 10 issue of the journal Nature, London's Times reports (Henderson, Times, 3/10). Bob Snow and colleagues at the University of Oxford used contemporary and historical epidemiological, geographical and demographic information as well as data from earth-orbiting satellites to model where people live, the likelihood of infection with Plasmodium falciparum malaria -- the deadliest form of the disease -- and susceptibility to developing the disease, according to BBC News (BBC News, 3/10). P. falciparum is "prevalent throughout the tropics" and has shown resistance to several drugs, according to London's Guardian (Radford, Guardian, 3/10). The researchers estimated that more than 500 million people were infected with P. falciparum malaria worldwide in 2002, 50% more than WHO has projected. Two-thirds of the cases occurred in Africa, mostly affecting children under five, but the researchers estimated that the number infected outside Africa was 200% higher than WHO estimates. Although the most dangerous strain of malaria is thought to be a problem "particular to Africa," the researchers showed that about 25% of cases occur in Southeast Asia and the West Pacific. The researchers estimated that about 2.2 billion people are at risk of contracting P. falciparum malaria worldwide (BBC News, 3/10). The researchers estimate that there were three times as many cases of P. falciparum malaria in Brazil and 1,000 times as many cases in Pakistan than the previous WHO estimates, according to VOA News.

Discrepancy
To predict the number of cases, WHO researchers gathered information about malaria cases in different regions of several African countries and then made estimates for each country as a whole. However, for countries outside Africa, WHO accepted government figures based on data from clinics. Snow said such government statistics are "inaccurate," according to VOA News. "You can't rely on national statistics to tell you the size of your disease burden," Snow said. Eline Korenromp of WHO's Roll Back Malaria Project -- which aims to reduce by half the number of malaria cases worldwide by 2010 -- said the agency will be adopting similar methods as those used by Snow and his colleagues, according to VOA News. "It is quite important to know the total burden of malaria, especially for allocating resources for fighting the disease," Korenromp said, adding, "It is also important to know how the disease burden is changing over time to see if countries are making progress and having an impact on the disease" (McAlary, VOA News, 3/10).

Reaction
The study results gave a "jolt" to health officials around the world, according to the Guardian (Guardian, 3/10). "Getting numbers right is important," Snow said, adding, "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 can't spend wisely. This is particularly important for new drugs needed to fight malaria." Richard Feachem, executive director of the Global Fund To Fight AIDS, Tuberculosis and Malaria, said, "This study is important," adding, "Many have believed that existing data grossly underestimates malaria, morbidity and mortality in Africa and Asia. We now have confirmation of this" (BBC News, 3/10). British Chancellor of the Exchequer Gordon Brown on Thursday urged developed countries to contribute more to fighting malaria in resource-poor countries, including "pumping money" into purchasing mosquito nets and a new malaria vaccine, according to the Scotsman (Churcher, Scotsman, 3/10). A new malaria vaccine tested on 2,000 children in Mozambique in 2004 offered "at least partial protection" against the disease, showing that an effective malaria vaccine is possible, according to the Guardian (Guardian, 3/10).