GLOBAL MALARIA SITUATION
I. DATA AVAILABILITY AND SOURCES
Since 2002, the WHO RBM Department has systematically compiled information on malaria burden and control in a global database. The contents of this database are available online via WHO’s Global Atlas of Infectious Disease. The present report is based on information from this database, as summarized below.
This report covers 107 malaria-endemic countries and territories, including a few that reported no malaria transmission in 2003 but which had reported malaria transmission within the time frame considered in this report (from 1990 to 2003).
Endemicity is defined as the probable presence of malaria transmission (Map 1 and Annex 5). Classifications of endemicity are not necessarily based on malaria cases and deaths reported in countries’ health information system (HIS). Several countries in North Africa, the Eastern Mediterranean and Central Asia, which have recently made tremendous progress in reducing transmission and are now within reach of eliminating malaria, were considered among the malaria-endemic countries. This was done because the confirmation of a malaria-free status or the absence of transmission is often difficult, awaiting codified measures for certification and continued vigilance.
Countries that have only imported cases or occasional local transmission— introduced cases resulting from imported cases—are not included, although surveillance of malaria cases and provision of access to effective antimalarial treatment remain important in these countries as well. This report focuses on countries with endemic malaria, and thus does not include information related to the burden of malaria among travellers or on prevention and treatment for this special population.
2. WHO annual malaria reporting
Each year, WHO regional offices request information from country officials and the NMCPs on a variety of areas related to malaria control. These include malaria cases and deaths from national HIS reported by various categorizations, drug policies and results of drug efficacy studies. Reporting also covers malaria-related services delivered by national control programmes, such as distribution and (re-)treatment of ITNs and houses sprayed for vector control during indoor residual spraying (IRS) campaigns. In addition, countries are asked for information on funds available for malaria control activities.
The aspects reported vary between regions as a result of regional differences in capacity for monitoring, existing reporting systems, and malaria epidemiology and control measures (Table 2).
Table 2. Aspects included in annual reporting from countries and territories to WHO regional offices  |
3. Reported cases and deaths from health information systems
In most countries, reported case rates represent only part of the actual total number of malaria cases, since many people are treated at home or in private facilities that do not report to the national HIS. Nevertheless, if HIS reporting is reasonably consistent and complete over the years, trends in reported cases might give some indication of the local trend in the malaria burden. Most countries with malaria outside Africa south of the Sahara report to WHO the number of cases recorded in their HIS during each year, with the exception of one missing report each in recent years from Belize and Haiti and occasional missing reports from Indonesia, Turkmenistan, Yemen and North African countries. Few countries in Africa south of the Sahara report malaria case rates every year (Table 3).
The definition of a reported case differs between countries and regions. In the Americas and in most countries of Asia, North Africa and Transcaucasia all reported cases are confirmed by laboratory diagnosis, usually microscopy. But in most countries in Africa south of the Sahara, cases are diagnosed and reported based on purely clinical grounds without laboratory testing (Annex 1 and Table A.21). For this reason, and because many African countries do not report any annual numbers of cases to WHO, trends in reported cases are not evaluated for Africa south of the Sahara.
Only in South-East Asia and the Western Pacific were malaria deaths reported with reasonable completeness over the years and by country. This report therefore reviews trends in reported death rates for these regions only.
Table 3. Number of malaria-endemic countries reporting malaria cases to WHO, by region and calendar year, 1990–2003  |
4. Monitoring antimalarial drug efficacy
Antimalarial drug resistance has become one of the greatest challenges in malaria control. In order to ensure the effective treatment of malaria, national drug policies must be regularly reviewed and revised as needed. These revisions are based on drug efficacy studies in sentinel sites that met a standardized WHO protocol (9); data from such studies are presented in this report. (Annex 1 gives definitions of drug efficacy; numbers of drug efficacy studies are in Section IV.)
5. Coverage of interventions through household surveys
The greatest burden of malaria and the greatest need for prevention and treatment occur in poorly accessible rural settings, where cases are often managed at home rather than in a formal health-care setting. Most people do not obtain their ITNs for protection against malaria from health facilities, and malaria patients seen in health facilities might not be representative of the people at risk of malaria in the population at large. For these reasons, household surveys are the most appropriate mechanism for monitoring the coverage of ITNs and the appropriate treatment for malaria in populations at risk.
Two major survey tools have provided the majority of population-level data for this report: Multiple Indicator Cluster Surveys (MICS) and Demographic and Health Surveys (DHS).
Multiple indicator cluster surveys
Between 1999 and 2001, MICS were conducted in 67 countries with support from UNICEF. MICS are nationally representative, with an average of around 6000 households sampled through a two-stage cluster design (10). The standard MICS questionnaire includes questions on possession and use of ITNs and use of antimalarial drugs for the treatment of fever for children under 5 years of age. MICS also provide data on all-cause under-5 mortality. Survey results and questionnaires are available on the Internet.
Demographic and health surveys
DHS are nationally representative household surveys that focus on reproductive and child health (11). Typically, DHS consist of interviews with 4000–12 000 women between 15 and 49 years of age living in households that are sampled in a multiplestage cluster design. Because the questionnaires are standardized and structured, DHS results are comparable between countries and over time. Since 1998, specific questions on malaria prevention and treatment have been included in DHS, where relevant. In addition to providing information on major RBM coverage indicators, DHS are a primary source of information on all-cause under-5 mortality rates. DHS are organized by Macro International, Calverton, MD, United States of America, and are funded primarily by the United States Agency for International Development (USAID). Questionnaires and survey results are available on the Internet approximately one year after completion of field work.
Over 50 MICS and DHS surveys contributed data on national-level ITN coverage for this report (Section IV and Annex 1). In addition, incidental national surveys conducted by health ministries were included. For countries where national surveys were lacking, high-quality cluster-sampled surveys conducted in subnational areas were considered. These included surveys conducted by the nongovernmental organizations (NGOs) NetMark (12) and Population Services International (PSI) (13).
6. Malaria-related commodities and service delivery
Service delivery measures are essential for interim progress evaluation between surveys of population coverage that occur only at approximately five-year intervals. In 2003, 41 of the 107 countries and territories with malaria reported on the number of nets (re-)treated with insecticide, 51 on nets sold or distributed, and 21 on the number of households sprayed. In addition, all WHO Member countries are asked to report annually on the quantities of insecticides used for vector control activities including against malaria vectors, according to guidelines published by the WHO Pesticide Evaluation Scheme (WHOPES). The latter information was comprehensively reported by WHO (14) and is summarized in this report.
WHO received data on national funds for malaria control from about half of the countries and territories (57 of 107) with malaria in 2003. Some of these countries also reported the different sources of the total budget. Information is not always comparable between countries because some numbers represent actually allocated funds, while others represent only budgeted funds. Interpreting available financial data is difficult given these inconsistencies, despite an overall improvement in the number of countries reporting since 2000 (Table 4).
Table 4. Number of countries reporting on funds for malaria control efforts, 1995–2003  |
The data described above are assembled in country profiles and regional tabulations (Annex 1 and Annex 2). In 2004, country profiles were sent to countries for comments and updating and to provide short descriptions of progress; 24 selected profiles from countries with a high malaria burden relative to the region to which they belong are included in this report. Additional profiles from all countries that provided information by 31 December 2004 to WHO are available on the RBM web site.
This report continues with a summary of the global malaria burden, followed by an overview of global control policies and strategies. Next, malaria burden and progress in control, including intervention coverage and drug efficacy data, are described separately for Africa, the Americas and Asia (including the Eastern Mediterranean and Transcaucasia) regions. These regions differ in malaria epidemiology, in the set of appropriate intervention strategies and in monitoring and evaluation systems. Therefore, the relevant indicators also differ. Regional summaries are followed by sections on global malaria control financing and global commodities and service delivery. The last section highlights gaps and limitations in the presented data and suggests ways for improving monitoring and evaluation at country, regional and global levels.
