title: Relationship between exposure, clinical malaria, and age in an area of changing transmission intensity.
abstract: The relationship between malaria transmission intensity and clinical disease is important for predicting the outcome of control measures that reduce transmission. Comparisons of hospital data between areas of differing transmission intensity suggest that the mean age of hospitalized clinical malaria is higher under relatively lower transmission, but the total number of episodes is similar until transmission drops below a threshold, where the risks of hospitalized malaria decline. These observations have rarely been examined longitudinally in a single community where transmission declines over time. We reconstructed 16 years (1991-2006) of pediatric hospital surveillance data and infection prevalence surveys from a circumscribed geographic area on the Kenyan coast. The incidence of clinical malaria remained high, despite sustained reductions in exposure to infection. However, the age group experiencing the clinical attacks of malaria increased steadily as exposure declined and may precede changes in the number of episodes in an area with declining transmission.
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, Maryland, USA. prudhomw@mail.nih.gov
authors.forename: Wendy P
authors.initials: WP
authors.lastname: O'Meara
authors.forename: Tabitha W
authors.initials: TW
authors.lastname: Mwangi
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Williams
authors.forename: F Ellis
authors.initials: FE
authors.lastname: McKenzie
authors.forename: Robert W
authors.initials: RW
authors.lastname: Snow
authors.forename: Kevin
authors.initials: K
authors.lastname: Marsh
mesh_terms: D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D006760:Hospitalization; D006776:Hospitals, Pediatric; D006801:Humans; D015994:Incidence; D007223:Infant; D007630:Kenya / Q000453:epidemiology; D008137:Longitudinal Studies; D008288:Malaria / Q000453:epidemiology* / Q000635:transmission; D011159:Population Surveillance; D015995:Prevalence; D012307:Risk Factors; D013997:Time Factors