[1] Turku Univ Hosp, Dept Pediat, POB 52, FIN-20520 Turku, Finland
[2] Univ Helsinki, Dept Virol, FIN-00290 Helsinki, Finland
[3] Helsinki Univ Hosp, Lab Div, Helsinki, Finland
[4] Turku City Hosp, Dept Geriatr, Turku, Finland
[5] Karolinska Univ Hosp, Dept Clin Microbiol, Stockholm, Sweden