Hyperparasitaemia is a marker of severe falciparum malaria. It is also apparent in severe knowlesi infections [3] , but is less commonly observed with severe vivax malaria. The 24 hr replicative cycle of asexual knowlesi may contribute to the rapidity with which hyperparasitaemia and clinical complications ensue. This shorter cycle compared with falciparum and vivax infections may overcome the reduced multiplicative capacity associated with the fewer merozoites generated by P. knowlesi (up to 16 per mature schizont) compared with P. falciparum (up to 36). Although up to 24 merozoites per schizont have been observed in Plasmodium vivax, parasitaemia is restricted to reticulocytes by limitation of invasion pathways in this species, rather than merozoite number.