1. Israel Institute for Biological Research, Ness Ziona, Israel; †Asaf Harofe Medical Center, Tzrifin, Israel; ‡Sheba Medical Center, Tel Hashomer, Israel; §Kaplan Hospital, Rehovot, Israel; ¶Bnei-Zion Medical Center, Haifa, Israel; #Schneider Children's Medical Center of Israel, Petach Tikvah, Israel; and **Centers for Disease Control and Prevention, Atlanta, Georgia, USA