Scaling Relationships

Malaria and Metrics across the Spectrum of Transmission Intensity

If we want to manage malaria, we need to measure it and set rational expectations about how changes in malaria transmission would affect the incidence of malaria and the prevalence of infection with malaria parasites. These ideas originate with Ronald Ross, and we can trace them forward through development of metrics to measure exposure, infection, disease, and mortality.

Exposure – We are interested in using the entomological inoculation rate (EIR) as our measure of exposure to understand malaria. In particular, we want to understand malaria in terms of the average annual EIR (aEIR), its seasonal pattern, and inter-annual variability.

Mosquitoes – The aEIR is related to mosquito population density

Exposure and Infection

Two measures of malaria are incidence and prevalence. Malaria prevalence, traditionally called the parasite rate (PR), can be measured at any point in time by taking a cross-sectional survey and examining blood for parasites using one of several diagnostics.

EIR-PR

Vignette: EIR-PR

A large data set describing paired estimates of the EIR and the PR was first published in a paper led by John Beier [1]. The data was expanded and it has been analyzed several times [14,SmithDL2005_EIRvPR?]. This website was designed, in part, to provide access to EIR-PR data in a way that could be updated and that would facilitate new analyses.

EIR-FoI

Vignette: EIR-FoI

George Macdonald reviewed the relationship between the EIR and the FoI for the first time in 1950 [MacdonaldG1950Epidemiology?]. A large data set describing paired estimates of the EIR and the FoI was first published in a paper led by me [SmithDL2010_InefficientTransmission?]. This website was designed, in part, to provide access to EIR-FoI data in a way that could be updated and that would facilitate new analyses.

Exposure and Disease

Exposure and Mortality

1.
Beier JC, Killeen GF, Githure JI. Short report: Entomologic inoculation rates and Plasmodium falciparum malaria prevalence in Africa. The American Journal of Tropical Medicine and Hygiene. 1999;61: 109–113. doi:10.4269/ajtmh.1999.61.109
2.
Hay SI, Guerra CA, Tatem AJ, Atkinson PM, Snow RW. Urbanization, malaria transmission and disease burden in Africa. Nat Rev Microbiol. 2005;3: 81–90. doi:10.1038/nrmicro1069
3.
Gething PW, Patil AP, Smith DL, Guerra CA, Elyazar IRF, Johnston GL, et al. A new world malaria map: Plasmodium falciparum endemicity in 2010. Malar J. 2011;10: 378. doi:10.1186/1475-2875-10-378
4.
Penny MA, Maire N, Bever CA, Pemberton-Ross P, Briët OJT, Smith DL, et al. Distribution of malaria exposure in endemic countries in Africa considering country levels of effective treatment. Malar J. 2015;14: 384. doi:10.1186/s12936-015-0864-3