[1] Riga Stradins Univ, Inst Microbiol & Virol, 5 Ratsupites St, LV-1067 Riga, Latvia
[2] Univ Helsinki, Dept Virol, 3 PL21, FIN-00014 Helsinki, Finland
[3] Childrens Clin Univ Hosp, 45 Vienibas Ave, LV-1004 Riga, Latvia
[4] Riga Stradins Univ, Dept Paediat, 16 Dzirciema St, LV-1067 Riga, Latvia