Parasitaemia profiles in a recrudescent infection. Patients with hyperparasitaemia are at greater risk of subsequent recrudescence even with fully sensitive parasites than patients with lower parasite densities. Each recrudescence provides an opportunity for enrichment (i.e. selection) of any resistant parasites formed. The total number of parasites in the body are shown on the lower vertical axis, drug concentrations of a slowly eliminated anti-malarial are shown in the upper panel. MIC: minimum inhibitory concentration.