[1] Turku Univ Hosp, Dept Pediat, FIN-20520 Turku, Finland
[2] Childrens Hosp, Dept Med, Boston, MA 02115 USA
[3] Univ Turku, Dept Virol, Turku, Finland
[4] Massachusetts Gen Hosp, Dept Emergency Med, Boston, MA 02114 USA
[5] Massachusetts Gen Hosp, Div Rheumatol Allergy & Immunol, Dept Med, Boston, MA 02114 USA