English: Countries where malaria is endemic as of 2003 Malaria generally occurs in areas where environmental conditions allow parasite multiplication in the vector. Thus, malaria is usually restricted to tropical and subtropical areas (see map) and altitudes below 1,500 m. However, this distribution might be affected by climatic changes, especially global warming, and population movements. Both Plasmodium falciparum and P. malariae are encountered in all shaded areas of the map (with P. falciparum by far the most prevalent). Plasmodium vivax and P. ovale are traditionally thought to occupy complementary niches, with P. ovale predominating in Sub-Saharan Africa and P. vivax in the other areas; however these two species are not always distinguishable on the basis of morphologic characteristics alone; the use of molecular tools will help clarify their exact distribution.