Population dynamics of a mixed Plasmodium vivax-P. falciparum infection, given a simultaneous appearance of the species (A), and a 10-day delay in P. falciparum appearance (B). As detailed in the text, an existing P. vivax infection can reduce peak levels of a subsequent P. falciparum superinfection (here from 10,100 to 7,400 parasites/μl). Here x = y = 0, cs = 0.001, cn = 0.001, ss = 0.001, sn = 0.1.