title: International dispersal of dengue through air travel: importation risk for Europe.
abstract: BACKGROUND
  The worldwide distribution of dengue is expanding, in part due to globalized traffic and trade. Aedes albopictus is a competent vector for dengue viruses (DENV) and is now established in numerous regions of Europe. Viremic travellers arriving in Europe from dengue-affected areas of the world can become catalysts of local outbreaks in Europe. Local dengue transmission in Europe is extremely rare, and the last outbreak occurred in 1927-28 in Greece. However, autochthonous transmission was reported from France in September 2010, and from Croatia between August and October 2010.
  
  
  METHODS
  We compiled data on areas affected by dengue in 2010 from web resources and surveillance reports, and collected national dengue importation data. We developed a hierarchical regression model to quantify the relationship between the number of reported dengue cases imported into Europe and the volume of airline travellers arriving from dengue-affected areas internationally.
  
  
  RESULTS
  In 2010, over 5.8 million airline travellers entered Europe from dengue-affected areas worldwide, of which 703,396 arrived at 36 airports situated in areas where Ae. albopictus has been recorded. The adjusted incidence rate ratio for imported dengue into European countries was 1.09 (95% CI: 1.01-1.17) for every increase of 10,000 travellers; in August, September, and October the rate ratios were 1.70 (95%CI: 1.23-2.35), 1.46 (95%CI: 1.02-2.10), and 1.35 (95%CI: 1.01-1.81), respectively. Two Italian cities where the vector is present received over 50% of all travellers from dengue-affected areas, yet with the continuing vector expansion more cities will be implicated in the future. In fact, 38% more travellers arrived in 2013 into those parts of Europe where Ae. albopictus has recently been introduced, compared to 2010.
  
  
  CONCLUSIONS
  The highest risk of dengue importation in 2010 was restricted to three months and can be ranked according to arriving traveller volume from dengue-affected areas into cities where the vector is present. The presence of the vector is a necessary, but not sufficient, prerequisite for DENV onward transmission, which depends on a number of additional factors. However, our empirical model can provide spatio-temporal elements to public health interventions.
authors.affiliation: European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden.
authors.forename: Jan C
authors.initials: JC
authors.lastname: Semenza
authors.affiliation: European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Sudre
authors.affiliation: Division of Infectious Diseases, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Miniota
authors.affiliation: European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Rossi
authors.affiliation: Division of Infectious Diseases, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Wei
authors.initials: W
authors.lastname: Hu
authors.affiliation: Division of Infectious Diseases, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Kossowsky
authors.affiliation: European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Suk
authors.affiliation: European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden.
authors.forename: Wim
authors.initials: W
authors.lastname: Van Bortel
authors.affiliation: Division of Infectious Diseases, St. Michael's Hospital, Toronto, Ontario, Canada; Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kamran
authors.initials: K
authors.lastname: Khan
mesh_terms: D000330:Aedes / Q000821:virology*; D064870:Air Travel / Q000706:statistics & numerical data*; D000818:Animals; D003715:Dengue / Q000453:epidemiology* / Q000635:transmission*; D003716:Dengue Virus / Q000302:isolation & purification*; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000821:virology*; D012306:Risk