1. National Institute of Health, 10-35 Kamiosaki 2-chome, Shinagawa-ku, Tokyo, Japan; Department of National Health and Welfare, Tunney's Pasture, Ottawa, Canada, K1A OL2; Shizuoka Public Health Laboratory, 3-6-2 Takajo-Cho, Shizuoka 420, Japan; PHLS Centre for Applied Microbiology and Research, Porton Down, Salisbury, Wiltshire, SP4 OJG, England; University of Georgia College of Agriculture, Experi