Effect of transmission intensity on outcome of IPTi. Qualitative depiction of the effect of transmission intensity on the age-incidence pattern of malaria morbidity and mortality. In areas of high transmission (solid line), malaria mortality is concentrated in the first two years of life. In areas of low or unstable transmission (dashed line), children may be at risk until much later in life. The arrows represent the window of greatest risk or the age interval during which roughly 75% of childhood malaria episodes are experienced.