The entomological inoculation rate and Plasmodium falciparum infection in African children

Abstract

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 diseases. 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 communities. 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.

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

a, The best fit for SIS (tan), SI°S (yellow), SI°RS (orange), the log-linear model (grey), and the best-overall model ∫SI°S (blue). The best-fit ∫SI°RS model was not visually different from the ∫SI°S model with heterogeneity. b, In ∫SI°S, PR is more sensitive to the variance in infection rates (that is, doubling or halving k) at high EIR (solid lines, blue and green), and more sensitive to variability in recovery (doubling or halving r) for low EIR (dashed lines, yellow and green). Models are defined in Methods.