[1] Univ Bonn, Med Ctr, Inst Virol, D-53127 Bonn, Germany
[2] Robert Koch Inst, Res Grp Emerging Zoonoses, D-13353 Berlin, Germany
[3] Robert Koch Inst, Ctr Biol Safety 1, D-13353 Berlin, Germany
[4] Chumakov Inst Poliomyelitis & Viral Encephalitide, Moscow, Russia