title: The geography of imported malaria to non-endemic countries: a meta-analysis of nationally reported statistics.
abstract: Malaria remains a problem for many countries classified as malaria free through cases imported from endemic regions. Imported cases to non-endemic countries often result in delays in diagnosis, are expensive to treat, and can sometimes cause secondary local transmission. The movement of malaria in endemic countries has also contributed to the spread of drug resistance and threatens long-term eradication goals. Here we focused on quantifying the international movements of malaria to improve our understanding of these phenomena and facilitate the design of mitigation strategies.
  
  
  
  In this meta-analysis, we studied the database of publicly available nationally reported statistics on imported malaria in the past 10 years, covering more than 50 000 individual cases. We obtained data from 40 non-endemic countries and recorded the geographical variations.
  
  
  
  Infection movements were strongly skewed towards a small number of high-traffic routes between 2005 and 2015, with the west Africa region accounting for 56% (13 947/24 941) of all imported cases to non-endemic countries with a reported travel destination, and France and the UK receiving the highest number of cases, with more than 4000 reported cases per year on average. Countries strongly linked by movements of imported cases are grouped by historical, language, and travel ties. There is strong spatial clustering of plasmodium species types.
  
  
  
  The architecture of the air network, historical ties, demographics of travellers, and malaria endemicity contribute to highly heterogeneous patterns of numbers, routes, and species compositions of parasites transported. With global malaria eradication on the international agenda, malaria control altering local transmission, and the threat of drug resistance, understanding these patterns and their drivers is increasing in importance.
  
  
  
  Bill & Melinda Gates Foundation, National Institutes of Health, UK Medical Research Council, UK Department for International Development, Wellcome Trust.
authors: WorldPop, Department of Geography and Environment, University of Southampton, Southampton, UK; Flowminder Foundation, Stockholm, Sweden. Electronic address: a.j.tatem@soton.ac.uk.
authors: Andrew J
authors: AJ
authors: Tatem
authors: Faculty of Geo-information Science and Earth Observation (ITC), University of Twente, Enschede, Netherlands.
authors: Peng
authors: P
authors: Jia
authors: WorldPop, Department of Geography and Environment, University of Southampton, Southampton, UK.
authors: Dariya
authors: D
authors: Ordanovich
authors: Department of Geography, University of Florida, Gainesville, FL, USA.
authors: Michael
authors: M
authors: Falkner
authors: Division of Infectious Diseases, Key Laboratory of Surveillance and Early-warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Beijing, China.
authors: Zhuojie
authors: Z
authors: Huang
authors: Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, UK; Centre for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA.
authors: Rosalind
authors: R
authors: Howes
authors: Institute for Health Metrics and Evaluation, University of Washington, Seattle WA, USA; Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK.
authors: Simon I
authors: SI
authors: Hay
authors: Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK.
authors: Peter W
authors: PW
authors: Gething
authors: Institute for Health Metrics and Evaluation, University of Washington, Seattle WA, USA; Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK.
authors: David L
authors: DL
authors: Smith
mesh_terms: D000354:Africa, Western / Q000453:epidemiology; D004351:Drug Resistance; D005602:France / Q000453:epidemiology; D062306:Geography, Medical / Q000706:statistics & numerical data*; D014943:Global Health / Q000706:statistics & numerical data; D006801:Humans; D008288:Malaria / Q000453:epidemiology* / Q000635:transmission; D010961:Plasmodium / Q000302:isolation & purification*; D014171:Transients and Migrants / Q000706:statistics & numerical data; D014195:Travel / Q000706:statistics & numerical data*; D006113:United Kingdom / Q000453:epidemiology