A severe mosquito-borne protozoan infection of the blood and blood-forming organs causing recurrent bouts of high fever due to the destruction of red blood corpuscles by plasmodia, malaria parasites. It is one of the world's greatest public health problems, affecting more than 200 million people and killing about 2 million every year, including more than 1 million children. Its long-term effects include hemolytic anemia, and it has devastating effects on other organs and tissues. It is now mainly a tropical and subtropical disease, but historically it has been endemic in cool temperate zones, wherever the anopheline mosquito vectors can exist. Current facts and figures and details of programs such as Roll Back Malaria are at http://www.who.int/topics/malaria/en/.