Review
Changes in the burden of malaria in sub-Saharan Africa

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Summary

The burden of malaria in countries in sub-Saharan Africa has declined with scaling up of prevention, diagnosis, and treatment. To assess the contribution of specific malaria interventions and other general factors in bringing about these changes, we reviewed studies that have reported recent changes in the incidence or prevalence of malaria in sub-Saharan Africa. Malaria control in southern Africa (South Africa, Mozambique, and Swaziland) began in the 1980s and has shown substantial, lasting declines linked to scale-up of specific interventions. In The Horn of Africa, Ethiopia and Eritrea have also experienced substantial decreases in the burden of malaria linked to the introduction of malaria control measures. Substantial increases in funding for malaria control and the procurement and distribution of effective means for prevention and treatment are associated with falls in malaria burden. In central Africa, little progress has been documented, possibly because of publication bias. In some countries a decline in malaria incidence began several years before scale-up of malaria control. In other countries, the change from a failing drug (chloroquine) to a more effective drug (sulphadoxine plus pyrimethamine or an artemisinin combination) led to immediate improvements; in others malaria reduction seemed to be associated with the scale-up of insecticide-treated bednets and indoor residual spraying.

Introduction

After a period of neglect, the urgent need to control malaria has once again engaged the attention of the international health community. Control of malaria is now on the political agenda of several of the world's wealthiest countries and funds have become available from the Global Fund to Fight AIDS, Tuberculosis and Malaria, The US President's Malaria Initiative, the World Bank, and bilateral donors on a scale not seen since the first attempted malaria eradication campaign in the 1950s and 1960s. The global fight against malaria is now being coordinated by the Roll Back Malaria Partnership, and major donor foundations, such as the Bill and Melinda Gates Foundation, have greatly increased financial support for malaria research. When compared with the low coverage of malaria control measures in 1999–2001,1 these investments have resulted in an increase in global production, procurement, distribution, and use of insecticide-treated bednets (ITNs). Global production more than tripled from 30 million in 2004 to 100 million in 2008. UNICEF procurement increased roughly 20-fold between 2000 and 2005 and has been stable since.2, 3 Ownership and use of ITNs within households, as measured by the number of children under 5 years of age reported to have used an ITN the previous night, increased by three to ten times between 2000 and 2008 in many African countries.2 There has also been an increase of about 25 times in the global procurement of artemisinin combination therapies (ACTs) in the past 5 years.2, 3

A renewed focus on elimination (cessation of local transmission of malaria within a defined geographical region) and eradication (global disappearance of one or more species of malaria parasite)4 has spurred several new initiatives, such as the Malaria Elimination Group, focusing on practical components of malaria elimination and the Malaria Eradication Research Agenda group setting the research agenda needed to support elimination and eradication.

This drive towards elimination has been encouraged by reports from several malaria endemic areas of declines in incidence of clinical cases and deaths. These changes have coincided with scale-up of effective prevention with ITNs and the use of more effective treatments for malaria in endemic areas. In some areas, additional vector-control measures, including indoor residual spraying and larval control have been deployed. The situation in Africa as a whole and how specific interventions have contributed to success stories is unclear. Therefore, we reviewed the relation between reported changes in the incidence or prevalence of malaria and the introduction or scale-up of specific interventions in several countries in sub-Saharan Africa. In this Review, we aim to identify common patterns and investigate whether factors other than these specific interventions might have contributed to the changes in malaria burden that have been reported.

13 key papers, which describe recent changes in malaria morbidity in sub-Saharan Africa were identified by consultation with experts. These papers were used as a guideline for a search for similar or related published studies. For each article reported we noted the: country, region, study period, population size, local endemicity, control measures and other factors independent of the study that might have affected transmission, rainfall data (if available), the type of data (ie, outpatient numbers, inpatient numbers, malaria mortality, prevalence), whether cases were slide confirmed, and the percentage change and the years of change for each type of data reported. The total number of malaria outpatients or inpatients for each reported year and the total number of deaths were also noted, when the information was available.

Section snippets

Changing malaria burden in sub-Saharan Africa

We identified studies that recorded trends in malaria indicators over time from countries in sub-Saharan Africa (figure 1, table). Most reports describe a recent decline in the incidence of malaria, the rest report little or no change.

Discussion

The burden of malaria has declined substantially in several areas of sub-Saharan Africa, particularly in the past 3–5 years, coinciding with expanding coverage of malaria prevention and treatment in many countries (figure 2). Country-wide surveillance in Ethiopia and Eritrea reveals a 70% decline in malaria morbidity, with similar changes documented in parts of Kenya, The Gambia, Rwanda, and Zambia. Malaria control on islands has been remarkably successful, even though the approaches used have

Conclusions

Reports from several countries in sub-Saharan Africa show a substantial, recent decline in the burden of malaria. Similar changes might have occurred in some other countries, for example Senegal, but these have not been reported in peer-reviewed publications. In other countries, there has probably been little change in the malaria burden. Successful control seems to have been achieved in several different ways, but it has sometimes proved difficult to link the timing of an apparent decline in

Search strategy and selection criteria

We searched the National Library of Medicine's Medline database with the Medical Subject Headings “Africa South of the Sahara”, “Malaria/epidemiology”, “Malaria/mortality”, “Malaria/prevention and control”, and “Malaria/transmission”, omitting papers that contained the keywords “Malaria/immunology”. The search was limited by restricting retrieval to articles published in the past 10 years. Our last search was done on March 29, 2010. The search identified 1528 publications. Articles were

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