title: The impact of urbanization and population density on childhood Plasmodium falciparum parasite prevalence rates in Africa.
abstract: Although malaria has been traditionally regarded as less of a problem in urban areas compared to neighbouring rural areas, the risk of malaria infection continues to exist in densely populated, urban areas of Africa. Despite the recognition that urbanization influences the epidemiology of malaria, there is little consensus on urbanization relevant for malaria parasite mapping. Previous studies examining the relationship between urbanization and malaria transmission have used products defining urbanization at global/continental scales developed in the early 2000s, that overestimate actual urban extents while the population estimates are over 15 years old and estimated at administrative unit level.
  
  
  
  This study sought to discriminate an urbanization definition that is most relevant for malaria parasite mapping using individual level malaria infection data obtained from nationally representative household-based surveys. Boosted regression tree (BRT) modelling was used to determine the effect of urbanization on malaria transmission and if this effect varied with urbanization definition. In addition, the most recent high resolution population distribution data was used to determine whether population density had significant effect on malaria parasite prevalence and if so, could population density replace urban classifications in modelling malaria transmission patterns. The risk of malaria infection was shown to decline from rural areas through peri-urban settlements to urban central areas. Population density was found to be an important predictor of malaria risk. The final boosted regression trees (BRT) model with urbanization and population density gave the best model fit (Tukey test p value <0.05) compared to the models with urbanization only.
  
  
  
  Given the challenges in uniformly classifying urban areas across different countries, population density provides a reliable metric to adjust for the patterns of malaria risk in densely populated urban areas. Future malaria risk models can, therefore, be improved by including both population density and urbanization which have both been shown to have significant impact on malaria risk in this study.
authors.affiliation: African Population and Health Research Centre, Nairobi, Kenya. ckabaria@aphrc.org.|Spatial Health Metrics Group, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi, Kenya. ckabaria@aphrc.org.
authors.forename: Caroline W
authors.initials: CW
authors.lastname: Kabaria
authors.affiliation: Spatial Epidemiology Laboratory, Université Libre de Bruxelles, CP160/12, Av. F.D. Roosevelt 50, 1050, Brussels, Belgium.|Fonds National de la Recherche Scientifique (F.R.S-FNRS), Brussels, Belgium.
authors.forename: Marius
authors.initials: M
authors.lastname: Gilbert
authors.affiliation: Spatial Health Metrics Group, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi, Kenya.|Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
authors.forename: Abdisalan M
authors.initials: AM
authors.lastname: Noor
authors.affiliation: Spatial Health Metrics Group, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi, Kenya.|Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Snow
authors.affiliation: Spatial Epidemiology Laboratory, Université Libre de Bruxelles, CP160/12, Av. F.D. Roosevelt 50, 1050, Brussels, Belgium.|Department of Geography, Université de Namur, Rue de Bruxelles 61, 5000, Namur, Belgium.
authors.forename: Catherine
authors.initials: C
authors.lastname: Linard
mesh_terms: D017954:Africa South of the Sahara / Q000453:epidemiology; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008270:Madagascar / Q000453:epidemiology; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000469:parasitology; D008297:Male; D010963:Plasmodium falciparum / Q000502:physiology*; D011156:Population Density; D015995:Prevalence; D012044:Regression Analysis; D014507:Urbanization
keywords: Boosted regression trees; Malaria; Population density; Urbanization