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Estimating Air Travel-Associated Importations of Dengue Virus Into Italy
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health. Institute of Public Health, University of Heidelberg, Heidelberg, Germany.
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2015 (English)In: Journal of Travel Medicine, ISSN 1195-1982, E-ISSN 1708-8305, Vol. 22, no 3, 186-193 p.Article in journal (Refereed) Published
Abstract [en]

Background: Southern Europe is increasingly at risk for dengue emergence, given the seasonal presence of relevant mosquito vectors and suitable climatic conditions. For example, Aedes mosquitoes, the main vector for both dengue and chikungunya, are abundant in Italy, and Italy experienced the first ever outbreak of chikungunya in Europe in 2007. We set out to estimate the extent of dengue virus importations into Italy via air travelers.

Methods: We attempted to quantify the number of dengue virus importations based on modeling of published estimates on dengue incidence in the countries of disembarkation and analysis of data on comprehensive air travel from these countries into Italy's largest international airport in Rome.

Results: From 2005 to 2012, more than 7.3 million air passengers departing from 100 dengue-endemic countries arrived in Rome. Our Importation Model, which included air traveler volume, estimated the incidence of dengue infections in the countries of disembarkation, and the probability of infection coinciding with travel accounted for an average of 2,320 (1,621–3,255) imported dengue virus infections per year, of which 572 (381–858) were “apparent” dengue infections and 1,747 (1,240–2,397) “inapparent.”

Conclusions: Between 2005 and 2012, we found an increasing trend of dengue virus infections imported into Rome via air travel, which may pose a potential threat for future emergence of dengue in Italy, given that the reoccurring pattern of peak importations corresponds seasonally with periods of relevant mosquito vector activity. The observed increasing annual trends of dengue importation and the consistent peaks in late summer underpin the urgency in determining the threshold levels for the vector and infected human populations that could facilitate novel autochthonous transmission of dengue in Europe.

Place, publisher, year, edition, pages
2015. Vol. 22, no 3, 186-193 p.
National Category
Public Health, Global Health, Social Medicine and Epidemiology
URN: urn:nbn:se:umu:diva-103205DOI: 10.1111/jtm.12192ISI: 000353382800008PubMedID: 25756472OAI: diva2:814219
Available from: 2015-05-26 Created: 2015-05-18 Last updated: 2016-03-30Bibliographically approved
In thesis
1. Imported infections’ importance: global change driving Dengue dynamics
Open this publication in new window or tab >>Imported infections’ importance: global change driving Dengue dynamics
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Vikten av importerade infektioner : kan globala förändringar förklara Dengue utbrott?
Abstract [en]

Background Dengue is a significant problem of international health concern. According to the World Health Organization in 2012, globally, dengue is “the most important mosquito borne viral disease” with incidence 30 higher than it had been 50 years ago. While most of the burden of disease associated with dengue is located in areas with a tropical and sub-tropical climate, increasing evidence suggests temperate areas are also at risk. Considering the recent introduction of relevant mosquito vectors into Southern Europe, and increasing numbers of imported dengue via travelers, Europe and other temperate areas may be increasingly at risk for dengue emergence, establishment and local transmission in the foreseeable future.

Methods Recent dengue emergence in Madeira and reemergence in Tokyo underline the hypothesis that passenger air-travel can be an important conduit for the importation of vector-borne disease leading to emergence in naïve areas climatically suitable for dengue transmission, including parts of Europe. Combining information on travel with virus genetic similarity was useful in discerning likely pathways of for the importation of infections. Generalizing information learned from outbreaks in Tokyo and Madeira with global epidemic intelligence, global travel networks, and climate change projections, leads to more refined understanding of the magnitude of dengue infectious imported into temperate areas and these virus introduction events’ potential implications for seeding epidemics in the 21st century.

Results While compared to total travel, imported dengue events and epidemics of dengue outside the tropics are rare, our combined evidence and modeled estimations suggest strongly that epidemic dengue emergence in temperate areas is possible and will continue to increase. We found that global change dynamics including warming temperatures in the much of the northern hemisphere and increasing passenger interconnectivity between areas endemic for dengue and dengue free areas are key mechanisms partly explaining these unprecedented epidemiological transitions.

Conclusion While we calibrated our models on information known about dengue, many elements of the methods and conclusions may increase understanding of the potentially global implications for imported infections of other climate-sensitive infectious diseases’ that may have similar parameters. During 2016 and the years to come, techniques developed in this doctoral research will contribute to models used in risk analysis for vector-borne diseases of interest, including the increasing important potential for imported Chikungunya and Zika viruses into a variety of unexposed areas. 

Place, publisher, year, edition, pages
Umeå: Umeå University, 2016. 99 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1793
Dengue, Zika, Vector-borne Disease, Aedes, Global Change, Climate Change, Viral Evolution, Phylogenetics, Travel, Interconnectivity, Disease Modeling, Madeira, Italy, Japan, Europe
National Category
Public Health, Global Health, Social Medicine and Epidemiology
urn:nbn:se:umu:diva-118645 (URN)978-91-7601-443-1 (ISBN)
Public defence
2016-04-22, Room 135, Building 9A, Northlands University Hospital (sal 135, byggnad 9A, Norrlands Universitetssjukhus), Umeå, Sweden, 13:00 (English)
EU, FP7, Seventh Framework Programme, 282589
Available from: 2016-03-31 Created: 2016-03-28 Last updated: 2016-04-20Bibliographically approved

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