[1] CTR DIS CONTROL & PREVENT, NATL CTR INFECT DIS, SCI RESOURCES PROGRAM, BIOTECHNOL CORE FACIL BRANCH, ATLANTA, GA 30333 USA
[2] DI IVANOVSKII INST VIROL, MOSCOW 123098, RUSSIA
[3] CHINESE ACAD PREVENT MED, INST VIROL, BEIJING 100052, PEOPLES R CHINA