title: Spatiotemporal clusters of malaria cases at village level, northwest Ethiopia.
abstract: BACKGROUND
  Malaria attacks are not evenly distributed in space and time. In highland areas with low endemicity, malaria transmission is highly variable and malaria acquisition risk for individuals is unevenly distributed even within a neighbourhood. Characterizing the spatiotemporal distribution of malaria cases in high-altitude villages is necessary to prioritize the risk areas and facilitate interventions.
  
  
  METHODS
  Spatial scan statistics using the Bernoulli method were employed to identify spatial and temporal clusters of malaria in high-altitude villages. Daily malaria data were collected, using a passive surveillance system, from patients visiting local health facilities. Georeference data were collected at villages using hand-held global positioning system devices and linked to patient data. Bernoulli model using Bayesian approaches and Marcov Chain Monte Carlo (MCMC) methods were used to identify the effects of factors on spatial clusters of malaria cases. The deviance information criterion (DIC) was used to assess the goodness-of-fit of the different models. The smaller the DIC, the better the model fit.
  
  
  RESULTS
  Malaria cases were clustered in both space and time in high-altitude villages. Spatial scan statistics identified a total of 56 spatial clusters of malaria in high-altitude villages. Of these, 39 were the most likely clusters (LLR = 15.62, p < 0.00001) and 17 were secondary clusters (LLR = 7.05, p < 0.03). The significant most likely temporal malaria clusters were detected between August and December (LLR = 17.87, p < 0.001). Travel away home, males and age above 15 years had statistically significant effect on malaria clusters at high-altitude villages.
  
  
  CONCLUSIONS
  The study identified spatial clusters of malaria cases occurring at high elevation villages within the district. A patient who travelled away from home to a malaria-endemic area might be the most probable source of malaria infection in a high-altitude village. Malaria interventions in high altitude villages should address factors associated with malaria clustering.
authors.affiliation: Department of Environmental and Occupational Health and Safety, Institute of Public Health, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia. alemukass@yahoo.com.
authors.forename: Kassahun
authors.initials: K
authors.lastname: Alemu
authors.forename: Alemayehu
authors.initials: A
authors.lastname: Worku
authors.forename: Yemane
authors.initials: Y
authors.lastname: Berhane
authors.forename: Abera
authors.initials: A
authors.lastname: Kumie
mesh_terms: D000293:Adolescent; D000328:Adult; D016000:Cluster Analysis; D005002:Ethiopia / Q000453:epidemiology; D006801:Humans; D008288:Malaria / Q000453:epidemiology* / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012424:Rural Population; D012621:Seasons; D062211:Spatio-Temporal Analysis; D055815:Young Adult