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The entomological inoculation rate and Plasmodium falciparum infection in African children


Malaria is an important cause of global morbidity and mortality. The fact that some people are bitten more often than others has a large effect on the relationship between risk factors and prevalence of vector-borne diseases1,2,3. Here we develop a mathematical framework that allows us to estimate the heterogeneity of infection rates from the relationship between rates of infectious bites and community prevalence. We apply this framework to a large, published data set that combines malaria measurements from more than 90 communities4. We find strong evidence that heterogeneous biting or heterogeneous susceptibility to infection are important and pervasive factors determining the prevalence of infection: 20% of people receive 80% of all infections. We also find that individual infections last about six months on average, per infectious bite, and children who clear infections are not immune to new infections. The results have important implications for public health interventions: the success of malaria control will depend heavily on whether efforts are targeted at those who are most at risk of infection.

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Figure 1: The data and fitted functions and a sensitivity analysis for the best overall model.

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We thank D. Bradley, B. Grenfell, F. E. McKenzie, W. Prudhomme, S. Randolph, M. Recker, D. Rogers and L. Waller for comments and suggestions. We also thank the NCEAS working group for discussion. S.I.H. is funded by a Research Career Development Fellowship from the Wellcome Trust. R.W.S. is a Wellcome Trust Senior Research Fellow and acknowledges the support of the Kenyan Medical Research Institute (KEMRI). This work was partially conducted as part of the Environment and Disease Working Group supported by the National Center for Ecological Analysis and Synthesis, a Center funded by NSF, the University of California Santa Barbara, and the State of California. The views presented in this Letter represent the personal views of the authors and do not construe or imply any official position or policy of the Fogarty International Center, National Institutes of Health, Department of Health and Human Services, or the US government. Author Contributions S.I.H. collated the data. D.L.S. designed and conducted the analysis. D.L.S., J.D., S.I.H. and R.W.S. wrote the paper.

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Smith, D., Dushoff, J., Snow, R. et al. The entomological inoculation rate and Plasmodium falciparum infection in African children. Nature 438, 492–495 (2005).

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