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Climate change and Aedes vectors: 21st century projections for dengue transmission in Europe
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health. Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore.
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
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2016 (English)In: EBioMedicine, ISSN 0360-0637, E-ISSN 2352-3964, Vol. 7, p. 267-277Article in journal (Refereed) Published
Abstract [en]

Warming temperatures may increase the geographic spread of vector-borne diseases into temperate areas. Although a tropical mosquito-borne viral disease, a dengue outbreak occurred in Madeira, Portugal, in 2012; the first in Europe since 1920s. This outbreak emphasizes the potential for dengue re-emergence in Europe given changing climates. We present estimates of dengue epidemic potential using vectorial capacity (VC) based on historic and projected temperature (1901–2099). VC indicates the vectors' ability to spread disease among humans. We calculated temperature-dependent VC for Europe, highlighting 10 European cities and three non-European reference cities. Compared with the tropics, Europe shows pronounced seasonality and geographical heterogeneity. Although low, VC during summer is currently sufficient for dengue outbreaks in Southern Europe to commence–if sufficient vector populations (either Ae. aegypti and Ae. albopictus) were active and virus were introduced. Under various climate change scenarios, the seasonal peak and time window for dengue epidemic potential increases during the 21st century. Our study maps dengue epidemic potential in Europe and identifies seasonal time windows when major cities are most conducive for dengue transmission from 1901 to 2099. Our findings illustrate, that besides vector control, mitigating greenhouse gas emissions crucially reduces the future epidemic potential of dengue in Europe.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 7, p. 267-277
Keyword [en]
Dengue, Vectorial capacity, Aedes aegypti, Aedes albopictus, Temperature, Climate change
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
URN: urn:nbn:se:umu:diva-118643DOI: 10.1016/j.ebiom.2016.03.046ISI: 000377459700039PubMedID: 27322480OAI: oai:DiVA.org:umu-118643DiVA: diva2:914935
Funder
EU, FP7, Seventh Framework Programme, 282589
Note

This study is part of the DengueTools project funded by the European Union Seventh Framework Programme FP7/2007-2013 under grant agreement no. 282589.

Originally included in thesis 1 as submitted manuscript.

Available from: 2016-03-28 Created: 2016-03-28 Last updated: 2018-01-10Bibliographically 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. p. 99
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1793
Keyword
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
Identifiers
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)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 282589
Available from: 2016-03-31 Created: 2016-03-28 Last updated: 2016-04-20Bibliographically approved
2. Climate Change, Dengue and Aedes Mosquitoes: Past Trends and Future Scenarios
Open this publication in new window or tab >>Climate Change, Dengue and Aedes Mosquitoes: Past Trends and Future Scenarios
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background Climate change, global travel and trade have facilitated the spread of Aedes mosquitoes and have consequently enabled the diseases they transmit (dengue fever, Chikungunya, Zika and yellow fever) to emerge and re-emerge in uninfected areas. Large dengue outbreaks occurred in Athens in 1927 and in Portuguese island, Madeira in 2012, but there are almost no recent reports of Aedes aegypti, the principal vector, in Europe. A dengue outbreak needs four conditions: sufficient susceptible humans, abundant Aedes vector, dengue virus introduction, and conducive climate. Can Aedes aegypti establish themselves again in Europe in the near future if they are introduced? How do the current and future climate affect dengue transmission globally, and regionally as in Europe? This thesis tries to answer these questions.

Methods Two process-based mathematical models were developed in this thesis. Model 1 describes a vector’s ability to transmit dengue – vectorial capacity – based on temperature and diurnal temperature range (DTR). Model 2 describes vector population dynamics based on the lifecycle of Aedes aegypti. From this model, vector abundance was estimated using both climate as a single driver, and climate together with human population and GDP as multiple drivers; vector population growth rate was derived as a threshold condition to estimate the vector’s invasion to a new place.

Results Using vectorial capacity, we estimate dengue epidemic potential globally for Aedes aegypti and in Europe for Aedes aegypti and Aedes albopictus. We show that mean temperature and DTR are both important in modelling dengue transmission, especially in a temperate climate zone like Europe. Currently, South Europe is over the threshold for dengue epidemics if sufficient dengue vectors are present. Aedes aegypti is on the borderline of invasion into the southern tip of Europe. However, by end of this century, the invasion of Aedes aegypti may reach as far north as the middle of Europe under the business-as-usual climate scenario. Or it may be restricted to the south Europe from the middle of the century if the low carbon emission – Paris Agreement – is implemented to limit global warming to below 2°C.

Conclusion Climate change will increase the area and time window for Aedes aegypti’s invasion and consequently the dengue epidemic potential globally, and in Europe in particular. Successfully achieving the Paris Agreement would considerably change the future risk scenario of a highly competent vector – Aedes aegypti’s – invasion into Europe. Therefore, the risk of transmission of dengue and other infectious diseases to the mainland of Europe depends largely on human efforts to mitigate climate change.

Abstract [sv]

Bakgrund Klimatförändringar tillsammans med en ökad frekvens av globala resor och handel har gynnat spridningen av Aedes-myggor och möjliggjort att de sjukdomar som de överför (dengue feber, Chikungunya, Zika och gul feber) etablerar sig i tidigare oinfekterade områden. Det två största utbrotten av dengue i Europa inträffade i Aten 1927 och på den portugisiska ön Madeira 2012 orsakades av Aedes aegypti, men i de allra flesta delar i Europa finns inga rapporter om Aedes aegypti. Ett utbrott av dengue kräver att fyra villkor uppfylls: tillräckligt mottagliga människor, rikligt med Aedes-vektorer, introduktion av dengue-virus, och ett gynnsamt klimat. En stor fråga idag är om Aedes aegypti kan etableras igen i Europa i ett förändrat klimat, och hur nuvarande och framtida klimatförhållanden möjligör dengue smittspridning globalt och regionalt i Europa. Denna avhandling försöker svara på dessa frågor.

Metoder Två processbaserade matematiska modeller utvecklades i arbetet med denna avhandling. En av modellerna beskriver vektorns förmåga att överföra dengue – vektorkapaciteten – baserat på temperatur och dyngstemperaturens varation (DTR). Den andra modellen beskriver vektorpopulationens dynamik baserat på myggans livscykel. Myggornas populationsdynamik och populationstäthet uppskattades med en modell baserat på enbart klimat, samt en modell baserat på klimat, mänsklig befolkning och BNP. Vektorgruppens tillväxthastighet härleddes som ett tröskelvärde för att uppskatta vektorernas invasionsbenägenhet till nya områden i takt med att klimatet förändras.

Resultat Med hjälp av vektorkapacitetmodellen uppskattade vi den epidemiska potentialen av dengue smittad av Aedes aegypti globalt och i Europa av Aedes aegypti och Aedes albopictus. Vi visar att den genomsnittliga temperaturen och DTR båda är viktiga för dengue myggornas kapacitet att starta epidemier, särskilt i tempererade klimatzoner, så som Europa. För närvarande är Syd-Europa tillräckligt gynnsamt för dengueepidemier vissa tider på året om myggpopulationerna är tillräckligt stora. Vi visat att Aedes aegypti möjligen kan etablera sig längs Europas södra utkanter idag. I slutet av detta århundrade kan invasionen av Aedes aegypti nå så långt norrut till mitten av Europa om vi inte begränsar klimatutsläppen mer än vad vi gör idag. Om vi följer klimatavtalet från Paris 2015 där den globala uppvärmningen begränsar till under 2 grader kan invasionen troligtvis förhindras, eller i vilket fall kraftigt begränsas i Europa.

Slutsats Ett varmare klimat kommer att öka antalet geografiska områdena i Europa som är gynnsamt för Aedes aegypti. Det kommer även öka tidsfönstret för vektorernas epidemiska potential globalt, och i synnerhet för Europa. En framgångsrik implementering av klimatavtalet från 2015, som riktar sig mot att begränsa uppvärmingen till under 2 grader, skulle väsentligt minska risken för en framtida invasion av dengue, zika och chikungunya i Europa. Därför beror risken för dengueöverföring och andra infektionssjukdomar i södra Europa till stor del på mänskliga ansträngningar för att med utsläppsminskningar av växthusgaser kontrollera klimatförändringen.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2018. p. 100
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1931
Keyword
dengue, mathematical modelling, vectorial capacity, DTR, Aedes aegypti, Aedes albopictus, climate change, Europe, vector invasion, abundance, dengue, matematisk modellering, vektorkapacitet, DTR, Aedes aegypti, Aedes albopictus, klimatförändring, Europa, vektor invasion
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Research subject
Epidemiology
Identifiers
urn:nbn:se:umu:diva-143764 (URN)978-91-7601-798-2 (ISBN)
Public defence
2018-02-02, Hörsal D, Tandläkarhögskolan, By1D, 9 tr, Norrlands universitetssjukhus, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2018-01-12 Created: 2018-01-09 Last updated: 2018-01-31Bibliographically approved

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