In endemic regions, where transmission is high, people are continuously infected so that they gradually develop an immunity to the disease. But until they have acquired such immunity, children remain highly vulnerable. Malaria is caused by parasites of the genus plasmodium , which are transmitted from one person to another by the female anopheline mosquito. The parasites develop in the gut of the mosquito, enter a victim's bloodstream via a mosquito bite and then invade and multiply in the liver. After nine to 16 days they return to the blood stream and infect the red blood cells, producing bouts of fever and anemia.
Cerebral malaria occurs when infected red cells obstruct the blood vessels in the brain.
Other vital organs can also be damaged often leading to the death of the patient. The search for a means of combatting malaria was given an impetus during World War II when thousands of soldiers from the US, Britain and Australia were sent to fight in infected areas in the Pacific and Asia. The powerful insecticidal effect of DDT was discovered and anti-malarial drugs of the chloroquine group were developed. While successful in large areas of North America, Southern Europe and the former Soviet Union, the disease persisted in Latin America and most Asian countries. The costs for the program were minimal, around 25 cents per person a year.