1. Department of Microbiology, State University of New York, Stony Brook 11794
2. Japan Poliomyelitis Research Institute, Higashimurayama, Tokyo 189, Japan
3. Department of Enteroviruses, National Institute of Health, Musashimurayama, Tokyo 190-12, Japan
4. Department of Microbiology, Faculty of Medicine, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan
5. National Institute for Public Health, Bilthoven, The Netherlands
6. Unité de Virologie Médicale, Institut Pasteur, 75724 Paris Cedex 15, France