Dengue virus infections among European travellers, 2015 to 2019

Background: Dengue is a disease with major impacts on public health in tropical and subtropical countries. In Europe, in the past decade, few autochthonous outbreaks were described. Aim: We aimed to identify factors associated with frequency of dengue virus infection among European travellers and at assess-ing how surveillance data could support prepared-ness against autochthonous outbreaks within Europe. Methods: We performed a descriptive analysis of travel-related dengue cases reported by European countries from 2015 through 2019. Using flight pas-senger data, we calculated travellers' infection rates (TIR). We investigated the following associations: (i) between TIR and incidence rate in selected countries of infection and (ii) between number of travel-related cases and occurrence of autochthonous outbreaks within Europe. Results: There were 11,478 travel-related dengue cases and the TIR was 2.8 cases per 100,000 travellers. Most cases were infected in Asia (71%), predominantly in south-eastern Asia. The TIR was highest among travellers returning from Asia (6.1/100,000). There was an association between the incidence rate in the country of infection and the TIR but no association between the number of travel-related cases and occurrence of autochthonous out-breaks in Europe. Conclusions: The likelihood of infection in travellers is a function of the ongoing epi-demiological situation in the country of exposure. The number of travel-related cases alone is not sufficient to estimate the likelihood of autochthonous outbreaks where vectors are present in Europe. Additional con-tributing factors such as adequate vectorial capacity and suitable environmental conditions are required.

Automated summary

This study aimed to identify factors associated with dengue virus infection among European travelers and assess how surveillance data could support preparedness against outbreaks in Europe. The study found that Asia was the most common region for dengue infection among travelers, with higher infection rates among travelers returning from Asia. There was an association between the incidence rate in the country of infection and the infection rate among travelers, but no association between the number of travel-related cases and occurrence of autochthonous outbreaks in Europe.