[1] US Dept HHS, Ctr Dis Control & Prevent, Publ Hlth Serv, Biol Branch,Sci Resources Program, Atlanta, GA 30333 USA
[2] US Dept HHS, Ctr Dis Control & Prevent, Publ Hlth Serv, Div Viral & Rickettsial Dis,Resp & Enter Viruses, Atlanta, GA 30333 USA
[3] Calif State Dept Hlth Serv, Div Communicable Dis Control, Viral & Rickettsial Dis Lab, Berkeley, CA USA