Date Published: June 15, 2010
Publisher: Public Library of Science
Author(s): Simon I. Hay, Emelda A. Okiro, Peter W. Gething, Anand P. Patil, Andrew J. Tatem, Carlos A. Guerra, Robert W. Snow, Ivo Mueller
Abstract: Simon Hay and colleagues derive contemporary estimates of the global clinical burden of Plasmodium falciparum malaria (the deadliest form of malaria) using cartography-based techniques.
Partial Text: Estimating the disease burden posed by malaria is an important public health challenge –. The clinical consequences of Plasmodium falciparum infection have several features that confound traditional approaches to disease burden and disability measurement ,. First, not all infections result in progression to disease, notably in areas of stable transmission , where populations have acquired clinical immunity . The overall risk of clinical disease has a curvilinear and uncertain association with the risk of infection as a combined function of age at first infection and immunity –. Second, the dominant symptom of fever, or other symptoms, does not distinguish malaria from other locally prevalent infections –. As a consequence, the routine reporting of “malaria” can overestimate disease rates by assuming that most fevers are malaria , and that fevers associated with an infection are causally linked to that infection ,. Third, with few exceptions across malaria-endemic countries, fevers or other malaria-like syndromes are often self-medicated and may resolve regardless of cause before reaching formal health systems . Fourth, inaccurate diagnoses ,, might be used to report disease rates, and these errors may be compounded through inadequate and incomplete national reporting systems –.
The combined clinical burden of the seven nations with comprehensive reporting was 3,367 cases in 2007 (Table 1, Protocol S2). Multiplying the population surface (Figure 3) by the assumed incidence rate in unstable areas (see Methods) produced an estimate of 105,395 clinical cases of P. falciparum malaria in areas of unstable transmission (Table 1, Protocol S2), with a plausible range between zero and 1,053,950. The modelling procedures in the stable areas generated an estimate of 451 million cases (lower 95% credible interval 349 million and upper 95% credible interval 552 million) of P. falciparum malaria in areas of stable transmission in 2007, of which 271 (241–301) million were estimated to have occurred in the Africa+ region, 177 (89–270) million in the CSE Asia region and 3 (1–7) million in the Americas (Table 1).
We have used a combination of methods, including a joint simulation of incidence in areas of stable transmission, to estimate 451 (349–552) million clinical cases of P. falciparum malaria in 2007: 3 (1–7) million in the Americas, 271 (241–301) in the Africa+ region, and 177 (89–270) in the CSE Asia region.