Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland

Number of tick-borne encephalitis (TBE) cases has increased and new foci have emerged in Finland during the last decade. We evaluated risk for locally acquired TBE in the capital region inhabited by 1.2 million people. We screened ticks and small mammals from probable places of TBE virus (TBEV) tran...

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Main Authors: Teemu Smura, Elina Tonteri, Anu Jääskeläinen, Gabriel von Troil, Suvi Kuivanen, Otso Huitu, Lauri Kareinen, Joni Uusitalo, Ruut Uusitalo, Tuula Hannila-Handelberg, Liina Voutilainen, Simo Nikkari, Tarja Sironen, Jussi Sane, Janne Castrén, Olli Vapalahti
Format: Article
Language:English
Published: Taylor & Francis Group 2019-01-01
Series:Emerging Microbes and Infections
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Online Access:https://www.tandfonline.com/doi/10.1080/22221751.2019.1612279
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author Teemu Smura
Elina Tonteri
Anu Jääskeläinen
Gabriel von Troil
Suvi Kuivanen
Otso Huitu
Lauri Kareinen
Joni Uusitalo
Ruut Uusitalo
Tuula Hannila-Handelberg
Liina Voutilainen
Simo Nikkari
Tarja Sironen
Jussi Sane
Janne Castrén
Olli Vapalahti
author_facet Teemu Smura
Elina Tonteri
Anu Jääskeläinen
Gabriel von Troil
Suvi Kuivanen
Otso Huitu
Lauri Kareinen
Joni Uusitalo
Ruut Uusitalo
Tuula Hannila-Handelberg
Liina Voutilainen
Simo Nikkari
Tarja Sironen
Jussi Sane
Janne Castrén
Olli Vapalahti
author_sort Teemu Smura
collection DOAJ
description Number of tick-borne encephalitis (TBE) cases has increased and new foci have emerged in Finland during the last decade. We evaluated risk for locally acquired TBE in the capital region inhabited by 1.2 million people. We screened ticks and small mammals from probable places of TBE virus (TBEV) transmission and places without reported circulation. The TBEV positive samples were sequenced and subjected to phylogenetic analysis. Within the study period 2007–2017, there was a clear increase of both all TBE cases and locally acquired cases in the Helsinki area. The surveillance of ticks and small mammals for TBEV confirmed four distinct TBEV foci in the Helsinki area. All detected TBEV strains were of the European subtype. TBEV genome sequences indicated that distinct TBEV lineages circulate in each focus. Molecular clock analysis suggested that the virus lineages were introduced to these foci decades ago. In conclusion, TBE has emerged in the mainland of Helsinki area during the last decade, with at least four distinct virus lineages independently introduced into the region previously. Although the overall annual TBE incidence is below the threshold for recommending general vaccinations, the situation requires further surveillance to detect and prevent possible further emergence of local TBE clusters.
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spelling doaj-art-faba366454a6494db5e99d844016436e2025-08-20T03:17:54ZengTaylor & Francis GroupEmerging Microbes and Infections2222-17512019-01-018167568310.1080/22221751.2019.1612279Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, FinlandTeemu Smura0Elina Tonteri1Anu Jääskeläinen2Gabriel von Troil3Suvi Kuivanen4Otso Huitu5Lauri Kareinen6Joni Uusitalo7Ruut Uusitalo8Tuula Hannila-Handelberg9Liina Voutilainen10Simo Nikkari11Tarja Sironen12Jussi Sane13Janne Castrén14Olli Vapalahti15Department of Virology, University of Helsinki, Helsinki, FinlandCenters for Military Medicine and Biothreat Preparedness, Helsinki, FinlandDivision of Clinical Microbiology, Helsinki University Hospital Laboratory Services (HUSLAB), Helsinki, FinlandArchipelago Doctors Ltd, Parainen, FinlandDepartment of Virology, University of Helsinki, Helsinki, FinlandNatural Resources Institute Finland (Luke), Helsinki, FinlandDepartment of Virology, University of Helsinki, Helsinki, FinlandDepartment of Virology, University of Helsinki, Helsinki, FinlandDepartment of Virology, University of Helsinki, Helsinki, FinlandCenters for Military Medicine and Biothreat Preparedness, Helsinki, FinlandCenters for Military Medicine and Biothreat Preparedness, Helsinki, FinlandCenters for Military Medicine and Biothreat Preparedness, Helsinki, FinlandDepartment of Virology, University of Helsinki, Helsinki, FinlandDepartment of Health Security, Infectious Disease Control and Vaccinations Unit, National Institute for Health and Welfare, Helsinki, FinlandArchipelago Doctors Ltd, Parainen, FinlandDepartment of Virology, University of Helsinki, Helsinki, FinlandNumber of tick-borne encephalitis (TBE) cases has increased and new foci have emerged in Finland during the last decade. We evaluated risk for locally acquired TBE in the capital region inhabited by 1.2 million people. We screened ticks and small mammals from probable places of TBE virus (TBEV) transmission and places without reported circulation. The TBEV positive samples were sequenced and subjected to phylogenetic analysis. Within the study period 2007–2017, there was a clear increase of both all TBE cases and locally acquired cases in the Helsinki area. The surveillance of ticks and small mammals for TBEV confirmed four distinct TBEV foci in the Helsinki area. All detected TBEV strains were of the European subtype. TBEV genome sequences indicated that distinct TBEV lineages circulate in each focus. Molecular clock analysis suggested that the virus lineages were introduced to these foci decades ago. In conclusion, TBE has emerged in the mainland of Helsinki area during the last decade, with at least four distinct virus lineages independently introduced into the region previously. Although the overall annual TBE incidence is below the threshold for recommending general vaccinations, the situation requires further surveillance to detect and prevent possible further emergence of local TBE clusters.https://www.tandfonline.com/doi/10.1080/22221751.2019.1612279Tick-borne encephalitisflavivirusincidencephylogenyFinland
spellingShingle Teemu Smura
Elina Tonteri
Anu Jääskeläinen
Gabriel von Troil
Suvi Kuivanen
Otso Huitu
Lauri Kareinen
Joni Uusitalo
Ruut Uusitalo
Tuula Hannila-Handelberg
Liina Voutilainen
Simo Nikkari
Tarja Sironen
Jussi Sane
Janne Castrén
Olli Vapalahti
Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland
Emerging Microbes and Infections
Tick-borne encephalitis
flavivirus
incidence
phylogeny
Finland
title Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland
title_full Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland
title_fullStr Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland
title_full_unstemmed Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland
title_short Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland
title_sort recent establishment of tick borne encephalitis foci with distinct viral lineages in the helsinki area finland
topic Tick-borne encephalitis
flavivirus
incidence
phylogeny
Finland
url https://www.tandfonline.com/doi/10.1080/22221751.2019.1612279
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