Assessing the infectious reservoir of falciparum malaria: past and future

Renewed interest in malaria eradication has placed greater emphasis on the development of tools to interrupt Plasmodium transmission, such as transmission-blocking vaccines. However, effective deployment of such tools is likely to depend on improving our understanding of which individuals transmit infections to mosquitoes. To date, only a handful of studies have directly determined the infectiousness of individuals in endemic populations. Here we review these studies and their relative merits. We also highlight factors influencing transmission potential that are not normally considered: the duration of human infectiousness, frequency of sampling by mosquitoes, and variation in vector competence among different mosquito populations. We argue that more comprehensive xenodiagnostic assessments of infectivity are necessary to accurately quantify the infectious reservoir and better target interventions.