malaria is a serious health problem.It is a leading cause of death in many countries.It occurs mostly in tropical and subtropical parts of the world,including parts of Africa,Asia,South America,Central America,and the Middle East.The place most intensely affected by malaria is Africa south of the Sahara Desert.About 60% of the world's malaria cases and 90% of malaria deaths occur there.Even though the causes of malaria in this region are well understood,international health agencies are finding that controlling it is still an enormous and difficult task