Mapping a decade of malaria prevalence in Africa

Maps tell stories. These can be stories of exploration and discovery, of politics and conflict, of imagination and art, and of science. The maps above are evidence-based representations of malaria prevalence in Africa. They come from a paper published in this week’s Lancet which compares the intensity of transmission of Plasmodium falciparum (the deadliest of the five species of malaria parasite that infect humans) in 49 countries or territories in Africa, between the years 2000 and 2010.

The article’s focus and its timing of publication are apt. Between 2000 and 2010, unprecedented investment was made to tackle malaria in Africa after the 1998 launch of the Roll Back Malaria Partnership, and in 2013 the World Health Organization set up the Malaria Situation Room, which identifies and seeks to solve issues preventing universal access to malaria control in the ten highest malaria burden countries in Africa. So as well as offering two data points to compare and contrast visually and statistically, the study provides a body of evidence which should prompt questions and influence efforts to tackle malaria in Africa going forward.

The maps display eight different malaria risk classes according to colour. Each colour corresponds to a level of risk of malaria being transmitted to humans. The scale runs from dark grey malaria-free areas, to dark green areas where over 75% of the population is infected.

Dr Abdisalan Noor at the KEMRI-Wellcome Trust Research Programme in Nairobi, Kenya, and his team sourced vast quantities of data about people in Africa who were examined for plasmodium infection since 1980. They then used predictive methods to plot malaria prevalence at distinct places and times. These methods had to be used because “health information systems in many African countries are weak”, Dr Noor explains, which makes it “difficult to reliably estimate how many people get sick, or die, of malaria”. The maps hide a wealth of statistics and algorithms, therefore, to show the real story of malaria in Africa.

What the study found

The two images appear strikingly similar at first glance. However, there are a number of differences hidden beneath. Focusing in on smaller sections, such as Zanzibar and Mayotte, shows areas with significant improvements. Zanzibar has moved from being largely at moderate-to-high risk of malaria in 2000 to low-to-moderate risk in 2010; and much of Mayotte has become malaria free in the ten years between 2000 and 2010.

Other changes are perhaps not immediate to the eye, but impressive to the mind: 40 of the 49 malaria endemic countries have become at least one level lower in terms of malaria risk; the number of people living in high risk regions fell by 35 million; and several countries’ levels of transmission have moved down in a way that merits a changing approach of dealing with malaria that can begin to focus on elimination.

While the overall story may be one of improvement, there are clear areas of concern – just ten countries account for 87% of people in the two highest risk classes for malaria, suggesting there is inconsistent progress in different areas; and with huge population growth the numbers living in moderate risk areas has grown by over 100 million to 280 million.

The bigger picture

Global funding for malaria control increased tenfold to over $2 billion in 2010,with efforts focusing on long-lasting insecticide-treated bednets (ITNs), indoor spraying of insecticides and prevention of malaria during pregnancy. Other factors influencing change include increasing urbanisation, the changing ways humans live together, improvements in socioeconomic status, and climate.

This new research raises a fundamental question of what malaria control in Africa should look like over the coming years. It provides a strong basis of data to support decisions, highlighting the importance of work on national and local levels, and the need to sustain progress where it has been made and to speed up work in areas where it hasn’t.

The study ends with a word of warning: “If investments in malaria are not sustained, hundreds of millions of Africans run the risk of rebound transmission, with catastrophic consequences”. The maps show a subtle picture of change – but they also offer a chance to use a body of data to go through old policies, to think up new ones and to come back and see what story malaria prevalence maps will be telling in another ten years’ time.

You can find the full paper on the Lancet website.