Dynamic patterns of Plasmodium vivax and P. falciparum populations in untreated mixed infections. As detailed in the text, particular ranges of parameters lead to patterns in which the two species oscillate nearly in phase with each other, with long periods in which both parasites may appear absent from the blood (A). Other ranges lead to out-of-phase oscillatory patterns, in which one species’ peak corresponds to the other’s trough (B). In A, x = y = 0, cs = 0.001, cn = 0.0001, ss = sn = 0.001; in B, x = y = 0, cs = 0.0001, cn = 0.01, ss = sn = 0.001.