Relapse commonly occurs between 8–24 weeks and is commonly seen with P. Reinfection cannot readily be distinguished from recrudescence, although recurrence of infection within two weeks of treatment for the initial infection is typically attributed to treatment failure.
Micrograph of a placenta from a stillbirth due to maternal malaria. Red blood cells are anuclear; blue/black staining in bright red structures (red blood cells) indicate foreign nuclei from the parasites.
According to a 2005 review, due to the high levels of mortality and morbidity caused by malaria—especially the P.
falciparum species—it has placed the greatest selective pressure on the human genome in recent history.
Several genetic factors provide some resistance to it including sickle cell trait, thalassaemia traits, glucose-6-phosphate dehydrogenase deficiency, and the absence of Duffy antigens on red blood cells.