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Estimating the global clinical burden of Plasmodium falciparum malaria in 2007

Estimating the global clinical burden of Plasmodium falciparum malaria in 2007
Estimating the global clinical burden of Plasmodium falciparum malaria in 2007
BACKGROUND: The epidemiology of malaria makes surveillance-based methods of estimating its disease burden problematic. Cartographic approaches have provided alternative malaria burden estimates, but there remains widespread misunderstanding about their derivation and fidelity. The aims of this study are to present a new cartographic technique and its application for deriving global clinical burden estimates of Plasmodium falciparum malaria for 2007, and to compare these estimates and their likely precision with those derived under existing surveillance-based approaches.

METHODS AND FINDINGS: In seven of the 87 countries endemic for P. falciparum malaria, the health reporting infrastructure was deemed sufficiently rigorous for case reports to be used verbatim. In the remaining countries, the mapped extent of unstable and stable P. falciparum malaria transmission was first determined. Estimates of the plausible incidence range of clinical cases were then calculated within the spatial limits of unstable transmission. A modelled relationship between clinical incidence and prevalence was used, together with new maps of P. falciparum malaria endemicity, to estimate incidence in areas of stable transmission, and geostatistical joint simulation was used to quantify uncertainty in these estimates at national, regional, and global scales. Combining these estimates for all areas of transmission risk resulted in 451 million (95% credible interval 349-552 million) clinical cases of P. falciparum malaria in 2007. Almost all of this burden of morbidity occurred in areas of stable transmission. More than half of all estimated P. falciparum clinical cases and associated uncertainty occurred in India, Nigeria, the Democratic Republic of the Congo (DRC), and Myanmar (Burma), where 1.405 billion people are at risk. Recent surveillance-based methods of burden estimation were then reviewed and discrepancies in national estimates explored. When these cartographically derived national estimates were ranked according to their relative uncertainty and replaced by surveillance-based estimates in the least certain half, 98% of the global clinical burden continued to be estimated by cartographic techniques.

CONCLUSIONS AND SIGNIFICANCE: Cartographic approaches to burden estimation provide a globally consistent measure of malaria morbidity of known fidelity, and they represent the only plausible method in those malaria-endemic countries with nonfunctional national surveillance. Unacceptable uncertainty in the clinical burden of malaria in only four countries confounds our ability to evaluate needs and monitor progress toward international targets for malaria control at the global scale. National prevalence surveys in each nation would reduce this uncertainty profoundly. Opportunities for further reducing uncertainty in clinical burden estimates by hybridizing alternative burden estimation procedures are also evaluated.
endemic diseases, statistics and numerical data, humansincidence, malaria, falciparum, epidemiology transmissionmodels, biological population surveillance methods, prevalence, reproducibility of results, uncertainty, world health
1549-1277
e1000290-[14pp]
Hay, S.I.
18d621e0-2813-4c05-b2b7-09df3f24aca7
Okiro, E.A.
24e6f33b-9321-4888-adfc-3380911e1dac
Gething, P.W.
82a5722c-21cc-462c-bdaf-7af4d50a6219
Patil, A.P.
3cdae3d1-307c-470b-8678-b1d188c045c0
Tatem, A.J.
6c6de104-a5f9-46e0-bb93-a1a7c980513e
Guerra, C.A.
112d8194-b5fd-43f0-a836-8617cb4c6fcd
Snow, R.W.
1df934dd-70f4-4bf1-8a98-7feb0207d796
Hay, S.I.
18d621e0-2813-4c05-b2b7-09df3f24aca7
Okiro, E.A.
24e6f33b-9321-4888-adfc-3380911e1dac
Gething, P.W.
82a5722c-21cc-462c-bdaf-7af4d50a6219
Patil, A.P.
3cdae3d1-307c-470b-8678-b1d188c045c0
Tatem, A.J.
6c6de104-a5f9-46e0-bb93-a1a7c980513e
Guerra, C.A.
112d8194-b5fd-43f0-a836-8617cb4c6fcd
Snow, R.W.
1df934dd-70f4-4bf1-8a98-7feb0207d796

Hay, S.I., Okiro, E.A., Gething, P.W., Patil, A.P., Tatem, A.J., Guerra, C.A. and Snow, R.W. (2010) Estimating the global clinical burden of Plasmodium falciparum malaria in 2007. PLoS Medicine, 7 (6), e1000290-[14pp]. (doi:10.1371/journal.pmed.1000290). (PMID:20563310)

Record type: Article

Abstract

BACKGROUND: The epidemiology of malaria makes surveillance-based methods of estimating its disease burden problematic. Cartographic approaches have provided alternative malaria burden estimates, but there remains widespread misunderstanding about their derivation and fidelity. The aims of this study are to present a new cartographic technique and its application for deriving global clinical burden estimates of Plasmodium falciparum malaria for 2007, and to compare these estimates and their likely precision with those derived under existing surveillance-based approaches.

METHODS AND FINDINGS: In seven of the 87 countries endemic for P. falciparum malaria, the health reporting infrastructure was deemed sufficiently rigorous for case reports to be used verbatim. In the remaining countries, the mapped extent of unstable and stable P. falciparum malaria transmission was first determined. Estimates of the plausible incidence range of clinical cases were then calculated within the spatial limits of unstable transmission. A modelled relationship between clinical incidence and prevalence was used, together with new maps of P. falciparum malaria endemicity, to estimate incidence in areas of stable transmission, and geostatistical joint simulation was used to quantify uncertainty in these estimates at national, regional, and global scales. Combining these estimates for all areas of transmission risk resulted in 451 million (95% credible interval 349-552 million) clinical cases of P. falciparum malaria in 2007. Almost all of this burden of morbidity occurred in areas of stable transmission. More than half of all estimated P. falciparum clinical cases and associated uncertainty occurred in India, Nigeria, the Democratic Republic of the Congo (DRC), and Myanmar (Burma), where 1.405 billion people are at risk. Recent surveillance-based methods of burden estimation were then reviewed and discrepancies in national estimates explored. When these cartographically derived national estimates were ranked according to their relative uncertainty and replaced by surveillance-based estimates in the least certain half, 98% of the global clinical burden continued to be estimated by cartographic techniques.

CONCLUSIONS AND SIGNIFICANCE: Cartographic approaches to burden estimation provide a globally consistent measure of malaria morbidity of known fidelity, and they represent the only plausible method in those malaria-endemic countries with nonfunctional national surveillance. Unacceptable uncertainty in the clinical burden of malaria in only four countries confounds our ability to evaluate needs and monitor progress toward international targets for malaria control at the global scale. National prevalence surveys in each nation would reduce this uncertainty profoundly. Opportunities for further reducing uncertainty in clinical burden estimates by hybridizing alternative burden estimation procedures are also evaluated.

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Published date: June 2010
Keywords: endemic diseases, statistics and numerical data, humansincidence, malaria, falciparum, epidemiology transmissionmodels, biological population surveillance methods, prevalence, reproducibility of results, uncertainty, world health
Organisations: University of Southampton, PHEW – P (Population Health)

Identifiers

Local EPrints ID: 344425
URI: http://eprints.soton.ac.uk/id/eprint/344425
ISSN: 1549-1277
PURE UUID: c88466d7-3f09-4672-b03c-5b6c21086e10
ORCID for A.J. Tatem: ORCID iD orcid.org/0000-0002-7270-941X

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Date deposited: 05 Nov 2012 13:59
Last modified: 15 Mar 2024 03:43

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Contributors

Author: S.I. Hay
Author: E.A. Okiro
Author: P.W. Gething
Author: A.P. Patil
Author: A.J. Tatem ORCID iD
Author: C.A. Guerra
Author: R.W. Snow

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