Rolling back malaria

Plasmodium falciparum is the most deadly of all malaria parasites. Children are particularly vulnerable to the devastating consequences of this infection, and the World Health Organisation (WHO) estimates that a child in Africa dies from malaria every minute (WHO, 2014). In recognition of this crisis, malaria has become a headline priority in global health, with campaigns such as the Roll Back Malaria initiative spearheading a huge international effort to tackle the disease. Abdisalan Noor and colleagues set out to assess how much progress has been made across Africa in the Roll Back Malaria era. Have the immense resources deployed made a real difference to some of the world’s most vulnerable populations? How has the burden of malaria altered in the decade since 2000? And can we identify whether infection risks have changed by country or region? With these questions in mind, Noor and colleagues developed a method to measure the changing patterns of malaria risk in Africa as precisely as possible (Noor et al., 2014). The symptoms of malaria can mimic those of many other infections, and suspected cases of malaria are often treated in the absence of a definite diagnosis and without attending a hospital or clinic. For these reasons, trying to get a clear picture of the scale of the malaria problem in Africa is a major challenge. Noor and colleagues chose to measure malaria by the most accurate method available, which involved looking for studies that had actually identified P. falciparum parasites in the blood. Their final analysis draws on data collected from 3.5 million individuals from over 26,000 surveys spanning 49 regions of Africa, with each piece of information linked to its precise geographic origin by satellite technology. The researchers—who are based at the Kenya Medical Research Institute-Wellcome Trust Research Programme in Nairobi, Oxford University and the WHO Regional Office for Africa in the Republic of Congo—fed this vast mine of data into a carefully constructed computational analysis. Each piece of information was adjusted to account for when and where it was collected, and the data were then standardized to work out the rate of infection in the age group of interest—the highly vulnerable population of children aged 2–10 years. They also factored in a host of complex influences on malaria transmission, such as urbanisation and climate. The final output was a measure of malaria risk for each individual square kilometre of Africa, first in 2000 and again a decade later. Each of these tiny squares was then classified into one of eight different malaria risk categories. From this analysis, Noor and colleagues report several substantial and encouraging improvements in the patterns of malaria in Africa. Strikingly, they calculated that 217 million people in Africa were living in a lower risk area in 2010 than they did in 2000. They also found an overall PHOTOGRAPH: AMAKA NWAGBARA