MAGDALENA WIECZOREK*, AGNIESZKA FIGAS and ARLETA KRZYSZTOSZEK National Institute of Public Health – National Institute of Hygiene, Department of Virology, Warsaw, Poland *Corresponding author: M. Wieczorek, National Institute of Public Health – National Institute of Hygiene, Department of Virology, Warsaw, Poland; e-mail: mrechnio@pzh.gov.pl. Submitted 30 July 2015, re...