1. Chumakov Institute of Poliomyelitis and Viral Encephalitides, Moscow, Russia
2. Institute of Virology, University of Bonn Medical Centre, Bonn, Germany
3. Khabarovsk Institute of Epidemiology and Microbiology, Khabarovsk, Russia
4. Center of Hygiene and Epidemiology in Khabarovsk Region, Khabarovsk, Russia
5. Centre International de Recherches Médicales de Franceville (CIRMF), Franceville, Gabon