MAGDALENA WIECZOREK*, ARLETA KRZYSZTOSZEK and AGNIESZKA WITEK. 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 21 August 2014, re...