1. Chumakov Institute of Poliomyelitis and Viral Encephalitides, Moscow, Russia
2. National Research Institute for Veterinary Virology and Microbiology of Russia, Pokrov, Vladimir Region, Russia
3. Institute of Virology, University of Bonn Medical Centre, Bonn, Germany
4. German Centre for Infection Research (DZIF), Bonn-Cologne, Germany