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 and is now established in numerous regions of Europe. Viremic travellers arriving in Europe from dengue-affected areas of the world can thus become catalysts of local outbreaks in Europe. 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 dengue importations into Europe and the volume of airline travellers arriving from dengue-affected areas worldwide. Results In 2010, over 5.8 million airline travellers entered Europe from dengue-affected areas worldwide. 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. During the active mosquito season 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 receive over 50% of all travellers from dengue-affected areas, yet with the continuing vector expansion due to conducive climatic conditions more cities will be implicated in the future. Conclusion The highest risk of dengue importation is restricted to few months, precisely when vector densities are the highest, and confined to a few cities. An expansion of the risk zone can be expected due to favourable climatic conditions for the vector. Our empirical model can provide a spatio-temporal element to public health interventions and can be used for early warning.
Highlights
Dengue has emerged as the most important viral mosquitoborne disease globally, taking on pandemic proportions with a 30fold increase in disease burden over the last half-century [1,2,3,4]
The adjusted incidence rate ratio for imported dengue into European countries was 1.09 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
The presence of the vector is a necessary, but not sufficient, prerequisite for dengue viruses (DENV) onward transmission, which depends on a number of additional factors
Summary
Dengue has emerged as the most important viral mosquitoborne disease globally, taking on pandemic proportions with a 30fold increase in disease burden over the last half-century [1,2,3,4]. Aedes aegypti is the predominant mosquito vector that transmits the dengue virus (four virus serotypes: DENV 1–4) to humans, whereas Aedes albopictus is a competent but less effective vector [8]. These vectors have expanded their habitat due to globalized travel and trade. In 2005 Ae. aegypti was first reported in Madeira, Portugal and has subsequently expanded over the southern part of the island [9]. Aedes albopictus is a competent vector for dengue viruses (DENV) and is established in numerous regions of Europe. Autochthonous transmission was reported from France in September 2010, and from Croatia between August and October 2010
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