The challenge of quantifying synchrony in malaria parasites

Malaria infection is often accompanied by periodic fevers, triggered by synchronous cycles of parasite replication within the host. Synchrony influences the efficacy of drugs and immune defenses and is therefore relevant to host health and infectiousness. Synchrony is thought to vary over the course of infection and across different hostparasite genotype or species combinations, but the evolutionary significance -if any- of this diversity remains elusive. Standardized methods are lacking, but the most common metric for quantifying synchrony is the percentage of parasites in a particular developmental stage. We use a heuristic model to show this metric is unacceptably biased. These methodological challenges must be addressed to characterize diverse patterns of synchrony and their consequences for disease severity and spread.