Figure 1

Long-latency P. vivax in the Netherlands; The mean monthly number of malaria cases in the village of Wormerveer, The Netherlands, recorded by Korteweg from 1902 to 1923 (black line) [15–17, 19]. Swellengrebel et al showed that malaria transmission usually occurred between the first week of August and the end of October [16]. From this it can be deduced that the initial wave of malaria cases derived from inoculations the previous year (pink curve) and, by subtraction, that this was followed by relapses and primary cases with a short incubation period in the late summer and autumn (blue curve) [19].