Malaria is endemic throughout most of the tropics. Of the approximately 3.4 billion people worldwide who are exposed annually, 1.2 billion are at high risk; the World Health Organization (WHO) states that more than 207 million developed symptomatic malaria in 2012 . Between 2000 and 2010, the number of reported annual malaria cases in 34 malaria-eliminating countries decreased by 85 percent from 1.5 million to 232,000 cases . Most of these are attributable to P. falciparum, but P. vivax and P. knowlesi can also cause severe disease. Malaria deaths peaked at 1.82 million in 2004 and fell to 1.24 million in 2010 (714,000 children <5 years and 524,000 individuals ≥5 years); over 80 percent of the deaths occur in sub-Saharan Africa . The WHO’s estimates of deaths from malaria (627,000 in 2012; uncertainty range 473,000 to 789,000) are approximately half the more reliable estimates above.
Important components for reducing the burden of malaria morbidity and mortality include more sensitive diagnostic tools, effective use of antimalarial drugs, and improved personal and community protection and mosquito control. The approach to elimination or control of malaria includes these basics, along with improvements in tracking of human illness and parasite surveillance, and effective resource delivery.
Issues related to epidemiology of malaria, including definitions and strategies for control, will be reviewed. Other related topics are discussed in detail separately. (See related topics.)
Malaria is transmitted via the bite of a female Anopheles spp mosquito, which occurs mainly between dusk and dawn. Other comparatively rare mechanisms for transmission include congenitally acquired disease, blood transfusion, sharing of contaminated needles, and organ transplantation [4,5].
Malaria occurs throughout most of the tropical regions of the world, with P. falciparum causing the largest burden of disease, followed by P. vivax (figure 1) . P. falciparum predominates in Africa, New Guinea, and Hispaniola (Haiti and the Dominican Republic); P. vivax is more common in the Americas and the western Pacific. The prevalence of these two species is approximately equal in the Indian subcontinent, eastern Asia, and Oceania (table 1) [7-9]. P. malariae is uncommon and is found in most endemic areas, especially in sub-Saharan Africa. P. ovale, even less common, is relatively unusual outside of Africa and, where it is found, comprises <1 percent of isolates. P. knowlesi, similar morphologically to P. malariae, has been identified by molecular methods in patients in Malaysia, the Philippines, Thailand, and Myanmar ; this species has not yet been proven to be transmitted from humans to mosquitoes (ie, a monkey reservoir may be required to infect mosquitoes).