Background: Although malaria is known to be a major cause of child mortality and morbidity throughout sub-Saharan Africa there are few detailed studies of malaria mortality rates and incidence of severe malarial disease in defined communities. We have studied the geographical pattern of admissions to hospital with severe malaria and the stability of this pattern over time in Kilifi District on the Kenyan Coast.
Methods: Over a 2-year period all children under 5 years of age with severe malaria admitted to the district hospital and living in a rural study population of about 50,000 people were identified. Annual censuses were carried out in the study area, and all households were mapped using a hand-held satellite navigation system. The resulting databases were linked using a geographical information system (GIS).
Results: Using methods originally developed for the study of the geographical distribution of childhood leukaemia we assessed the spatial pattern of hospital admission rates for severe malaria. As expected, admission rates were significantly higher in children with easier access to the hospital. For example, those living more than 25 km from the hospital had admission rates which were about one-fifth of those for children living within 5 km of the hospital. Those living more than 2.5 km from the nearest road had admission rates that were about half of those for children living within 0.5 km of a road. We also investigated short-term local fluctuations in severe malaria and found evidence of space-time clustering of severe malaria.
Conclusions: Hospital admission rates for severe malaria are higher in households with better access to hospital than in those further away. The finding of space-time clusters of severe malaria suggests that it would be of value to conduct case-control studies of environmental, genetic and human behavioural factors involved in the aetiology of the disease.
PIP: To investigate the geographic pattern of severe malaria and the stability of this pattern over time, all 358 children under 5 years of age admitted to a district hospital in Kenya's Kilifi District with severe malaria in 1991-93 and living in a rural study population of about 50,000 people were identified. All households were mapped through use of a hand-held satellite navigation system and the resulting databases were linked through a geographic information system. Area-specific rates showed evidence of association between the two years, suggesting that the pattern of disease was to some extent stable over time. As expected, hospital admissions for malaria were significantly higher in children with easier access to the hospital. Those living more than 25 km from the hospital had admission rates about one-fifth those for children living within 5 km of the hospital. Those living more than 2.5 km from the nearest road had admission rates about half those for children within 0.5 km of a road. Investigation of short-term local fluctuations in severe malaria revealed evidence of space-time clustering of severe malaria, supporting the view that severe malaria tends to occur in localized micro-epidemics. Recommended are case-control studies of environmental, genetic, and human behavioral factors involved in the etiology of the disease.