I heard her cries before I saw her. Rita* is a slight girl, maybe eight years old, and she has malaria. In this part of West Africa – a far northern corner of Ghana, near the border with Burkina Faso – the most likely culprit is the parasite Plasmodium falciparum that causes the deadliest type of malaria. Rita emerged from the clinic: teary-eyed, exhausted, miserable. She walked slowly and unsteadily beside her mother, and then dropped to the floor and vomited.