[1] Univ Calif Los Angeles, Los Angeles, CA 90024 USA
[2] Los Alamos Natl Lab, Los Alamos, NM USA
[3] Armed Forces Inst Pathol, Washington, DC 20306 USA
[4] Ctr Dis Control & Prevent, WHO, Collaborating Ctr Influenza, Atlanta, GA USA
[5] Victoria Univ, WHO, Collaborating Ctr Influenza, Parkville, Vic, Australia
[6] Natl Inst Med Res, MRC, WHO, Collaborating Ctr Influenza, London NW7 1AA, England
[7] Natl Inst Infect Dis, WHO, Collaborating Ctr Influenza, Tokyo, Japan
[8] WHO, Influenza Program, CH-1211 Geneva, Switzerland