New malaria maps
Authors: Francois H Nosten, Aung Pyae Phyo
Journal: The Lancet (2019)

In The Lancet, Katherine Battle1Battle KE Lucas TCD Nguyen M et al.Mapping the global endemicity and clinical burden of Plasmodium vivax, 2000–17: a spatial and temporal modelling study.Lancet. 2019; published online June 19. http://dx.doi.org/10.1016/S0140-6736(19)31096-7Summary Full Text Full Text PDF Scopus (159) Google Scholar and Daniel Weiss2Weiss DJ Lucas TCD Nguyen M et al.Mapping the global prevalence, incidence, and mortality of Plasmodium falciparum, 2000–17: a spatial and temporal modelling study.Lancet. 2019; published online June 19. http://dx.doi.org/10.1016/S0140-6736(19)31097-9Summary Full Text Full Text PDF Scopus (180) Google Scholar and colleagues present new malaria maps. These maps are the result of a considerable effort and will undoubtedly be well received by individuals interested in malaria. Several novelties and improvements from earlier versions are noticeable: the data for Plasmodium falciparum now cover the entire endemic world and include 5 km × 5 km pixel-level maps of mortality. Importantly, these are the first dynamic maps on Plasmodium vivax and for both plasmodial species; they include a time series spanning from 2000 to 2017. Overall, the new malaria maps support the decline in morbidity of both malaria species and mortality of P falciparum worldwide, but also point toward problematic regions where malaria transmission is persisting, or even increasing.3WHOWorld Malaria Report 2018. Geneva, World Health Organization.https://www.who.int/malaria/publications/world_malaria_report/en/Date: 2017Date accessed: April 30, 2019Google Scholar Maps revealing spatiotemporal variations in endemicity of both parasite species are useful for estimating the disease burden, quantifying the effect of control efforts, and assessing the achievability and progress towards elimination. The enthusiastic reader looking at these colourful, interactive, high-resolution maps will be tempted to quickly zoom-in at a particular area of interest. But caution is required for several reasons. Firstly, the data presented are the results of complex mathematical models and do not necessarily represent the actual truth on the ground. Secondly, the user should pay attention to the statistical uncertainties around the estimates and carefully examine the corresponding uncertainty maps provided. A quick look at the malaria incidence in the WHO reports shows large and unexplained variations from year to year in some regions3WHOWorld Malaria Report 2018. Geneva, World Health Organization.https://www.who.int/malaria/publications/world_malaria_report/en/Date: 2017Date accessed: April 30, 2019Google Scholar and some recent modelling gave different estimates for the Greater Mekong Subregion.4Maude RJ Mercado CEG Rowley J et al.Estimating malaria disease burden in the Asia-Pacific.Wellcome Open Res. 2019; 59: 1-17Google Scholar Thirdly, the well known heterogeneity of malaria transmission is difficult to visualise on global maps and these are the best compromise possible. Country-level maps scaled by local data should be available on the Malaria Atlas Project website upon publication. Finally, one will need to digest the unusually large amount of information contained in the appendix, to fully comprehend the limitations of the information provided. Examples of limitations include, among others, the absence of accessible data in some countries, the role of the private sector in treating malaria cases, the border effect when visualising data from two different countries, as well as the difficulties in estimating the burden of P vivax in Africa, where data were not usually collected until recently, and where there is uncertainty with Duffy positive populations, which are susceptible to P vivax malaria. The data provided for P vivax are truly novel and important. However, for Africa, the numbers are derived by converting P falciparum incidence using the species ratio from the World Malaria Report,3WHOWorld Malaria Report 2018. Geneva, World Health Organization.https://www.who.int/malaria/publications/world_malaria_report/en/Date: 2017Date accessed: April 30, 2019Google Scholar assuming that the spatial pattern of transmission is broadly similar for the two species. This factor is a clear limitation outside of the Horn of Africa where subnational surveillance data are available. The authors do acknowledge that these new malaria maps could underestimate low-density infections not detected by conventional diagnostics and liver stage infections of P vivax. Researchers, policy makers, national programmes, funders, and the media will undoubtedly find these maps and associated tools useful for monitoring spatial and time trends and for planning purposes. How useful they are for targeted interventions is less clear. This uncertainty is because of the above mentioned limitations but also because of the scarcity of good-quality data at subnational levels. Good intelligence is key in the fight against malaria, especially in the context of elimination of P falciparum. But data for disease burden are intractably linked to funding and individuals who are looking for funding for malaria programmes could be tempted to manipulate numbers. Let us hope, with the authors of this magnificent work, that these maps will stimulate more data sharing from all individuals involved so that the accuracy, precision, and usefulness of these tools continue to improve in the coming years. This online publication has been corrected. The corrected version first appeared at thelancet.com on July 1, 2019 This online publication has been corrected. The corrected version first appeared at thelancet.com on July 1, 2019 We declare no competing interests. Mapping the global endemicity and clinical burden of Plasmodium vivax, 2000–17: a spatial and temporal modelling studyOur study highlights important spatial and temporal patterns in the clinical burden and prevalence of P vivax. Amid substantial progress worldwide, plateauing gains and areas of increased burden signal the potential for challenges that are greater than expected on the road to malaria elimination. These results support global monitoring systems and can inform the optimisation of diagnosis and treatment where P vivax has most impact. Full-Text PDF Open AccessMapping the global prevalence, incidence, and mortality of Plasmodium falciparum, 2000–17: a spatial and temporal modelling studyHigh-resolution maps of P falciparum provide a contemporary resource for informing global policy and malaria control planning, programme implementation, and monitoring initiatives. Amid progress in reducing global malaria burden, areas where incidence trends have plateaued or increased in the past 5 years underscore the fragility of hard-won gains against malaria. Efforts towards elimination should be strengthened in such areas, and those where burden remained high throughout the study period. Full-Text PDF Open AccessDepartment of ErrorNosten FH, Pyae Phyo A. New malaria maps. Lancet 2019; 394: 278–79—In this Comment, the spelling of author Aung Pyae Phyo's name was incorrect. This correction has been made to the online version as of July 1, 2019, and the printed version is correct. Full-Text PDF