wiki:infection:malaria

Malaria

The 5 species of malaria parasites now known to affect humans differ in their geographic distribution:

Plasmodium falciparum	most common in sub-Saharan Africa and Melanesia (Papua New Guinea and the Solomon Islands)	can cause rapidly progressive and severe illness and death
P. vivax	mainly Central and South America, North Africa, the Middle East and within the Indian subcontinent	less severe but treatment for hypnozoites which lie dormant in the liver is necessary to help prevent relapses
P. ovale	almost exclusively in West Africa
P. malariae	mainly in Africa.
P. knowlesi	on the island of Borneo and other parts of South-East Asia	can cause rapidly progressive and severe illness and death

Thick blood smears are more sensitive in detecting malaria parasites because the blood is more concentrated
-ve blood smear makes diagnosis of malaria unlikely but non-immune individuals may be symptomatic at very low/indetectable parasite densities, therefore blood smears should be repeated every 12-24/24 x3 before ruling out Dx.
Rapid antigen test also available but less sensitive
PCR test more sensitive and specific than microscopy