Assessing the risk of importing dengue and chikungunya viruses to the European Union.

OBJECTIVE

A competent vector of dengue and chikungunya viruses, Aedes albopictus, is present in Europe. As a first step towards assessing the likelihood of local transmission of these viruses in Europe, we estimated the number of viremic person-days among air-travellers arriving in the European Union (EU).

METHODS

For dengue, we developed a Monte Carlo model with the following parameters: probability distributions based on quarterly incidences in endemic countries (years 2003-2007), passenger flow from endemic to EU countries (year 2006), duration of viremia, probability of being viremic upon arrival, distribution and period of vector activity in the EU. For chikungunya, due to scarce incidence data, we developed a model with point estimates.

RESULTS

We estimated at 4763 (range 3067-7019) the median dengue viremic person-days in 2006 with highest estimate among travellers from Asia during the third quarter. Dengue estimates among travellers arriving in EU Aedes-infested areas from April to October were 169 viremic person-days, 130 arriving in Italy. For chikungunya, we estimated 6 viremic person-days in EU Aedes-infested areas among air-travellers from India; all occurred in Italy.

CONCLUSION

Our results are a first step towards a real estimation of the risk of local dengue transmission in Europe. Further research is needed to better understand vector capacity and other factors related to virus transmission in temperate climates. Information on personal protection to travellers, early diagnosis and implementation of vector monitoring and control should be a priority in EU areas where the vector is established.