The ears of the hippopotamus: manifestations, determinants, and estimates of the malaria burden

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Malarious patients experience asymptomatic parasitemia; acute febrile illness (with cerebral damage, anemia, respiratory distress, hypoglycemia); chronic debilitation (anemia, malnutrition, nervous system-related sequelae); and complications of pregnancy (anemia, low birth weight, increased infant mortality). These manifestations in patients, communities, and countries reflect intrinsic (human, parasite, mosquito) and extrinsic (environmental, social, behavioral, political, and economic conditions as well as disease-control efforts) determinants. At a minimum, between 700,000 and 2.7 million persons die yearly from malaria, over 75% of them African children. Between 400 and 900 million acute febrile episodes occur yearly in African children under 5 yr of age living in endemic areas. Although about half of these children are parasitemic, all merit consideration of malaria-specific therapy, which is becoming more problematic because of parasite resistance to drugs. These numbers will more than double over the next 20 yr without effective control. Fewer than 20% of these febrile episodes and deaths come to the attention of any formal health system. The relatively few ill patients who have any contact with the health services represent the "ears of the hippopotamus." Greatly intensified research activities and control of the intolerable burden of malaria are mandatory if economic development is to accelerate in Africa. In particular, support should be targeted to understanding and preventing malaria-induced anemia, hypoglycemia, effects on pregnancy, and neurologic and developmental impairment. To decrease and stop transmission of this intolerable scourge, there is an urgent need for malaria vaccines, newer drugs, and better vector control methods as well as the ability to improve current technologies and use them more efficiently.