AGNIESZKA FIGAS, MAGDALENA WIECZOREK, BOGUMIŁA LITWIŃSKA and WŁODZIMIERZ GUT National Institute of Public Health – National Institute of Hygiene, Department of Virology, Warsaw, Poland *Corresponding author: A. Figas, National Institute of Public Health – National Institute of Hygiene, Department of Virology, Warsaw, Poland; e-mail: awitek@pzh.gov.pl. Submitted 14 December 2...