Tick-borne Encephalitis Virus in Wild Rodents in Winter, Finland, 2008–2009
Elina Tonteri, Anu E. Jääskeläinen , Tapani Tikkakoski, Liina Voutilainen, Jukka Niemimaa, Heikki Henttonen, Antti Vaheri, and Olli Vapalahti
Author affiliations: Author affiliations: University of Helsinki, Helsinki, Finland (E. Tonteri, A.E. Jääskeläinen, L. Voutilainen, A. Vaheri, O. Vapalahti); Karolinska Institutet, Solna, Sweden (E. Tonteri); Keski-Pohjanmaa Central Hospital, Kokkola, Finland (T. Tikkakoski); Finnish Forest Research Institute, Vantaa, Finland (L. Voutilainen, J. Niemimaa, H. Henttonen); Hospital District of Helsinki and Uusimaa, Helsinki (O. Vapalahti)
Figure 2. Monthly day and night mean temperatures at the trapping sites. Daily maximum temperatures had not reached 5°C for >50 days before trapping. Tick-feeding season is considered to begin when temperature in the ground reaches the tick activity limit and stays above it (1). A) Kokkola archipelago, where Siberian subtype of tick-borne encephalitis virus is endemic. B) Helsinki archipelago, where European subtype of tick-borne encephalitis virus is endemic. Although trapping was conducted on Isosaari, temperature data were unavailable and were instead collected on Harmaja, a nearby island (Figure 1). Gray bars indicate time of trapping; red line indicates tick activity limit. Data source: Finnish Meteorological Institute (http://ilmatieteenlaitos.fi/en/).
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