The pathophysiology of severe knowlesi malaria in humans is undescribed, but nonetheless important for several reasons. First, to provide improved guidelines for the diagnosis, treatment and management of severe knowlesi cases. Secondly, when severe knowlesi infection is compared with severe falciparum malaria, this can help clarify determinants of severe disease. Thirdly, it is possible that we are observing a P. knowlesi vertebrate host switch from Southeast Asian macaques to a fullblown emergence into the human population [11, 12] . Therefore, it is important to understand properly the disease caused by P. knowlesi to assist strategies to reduce health-impacts if human-to-human transmission of this virulent pathogen is established.