Malaria

Malaria is easily misdiagnosed because it resembles many other diseases. Early symptoms include malaise, fatigue, headache, nausea and vomiting, and muscular aches; after several hours, the characteristic high fever and chills occur. The body's principal defenses are fever and filtration of infected red blood cells in the spleen. Neither of these mechanisms, however, is completely effective in ridding the body of the parasite.

P. falciparum is the most dangerous of the four malaria strains, and can kill a healthy adult in 48 hours. This type is so dangerous because the parasitized red blood cells become sequestered in the deep vascular beds of the brain—hence the term "cerebral malaria" for infection with this strain. Sequestration happens because parasite-derived proteins on the surface of infected red blood cells cause them to stick to each other and to the cells lining the host's venules and capillaries (two types of small blood vessel), especially in the brain and heart. This has the effect of keeping the parasite away from the host's natural defense system. It also means that the progress of the disease can be hidden from a health practitioner who draws blood from a peripheral body region (for example, the arm); such blood will not reveal the true extent of the infection. Delirium, convulsions, and coma are features of falciparum malaria, which is associated with a 20% mortality rate in adults.