1. The Rockefeller University, New York, New York.
2. National Institute of Public Health, Prague, Czech Republic.
3. Bacteriology Division, Adolfo Lutz Institute, São Paulo, Brazil.
4. Central Public Health Laboratory, Montevideo, Uruguay.
5. Instituto Nacional de Salud, Bogotá, Colombia.
6. Instituto Nacional de Enfermedades Infecciosas, A.N.L.I.S. "Dr. C. Malbrán," Buenos Aires, Argentina.
7. Instituto Nacional de Salud Pública, Cuernavaca, Morelos, México.
8. St. Laszlo Hospital for Infectious Diseases, Budapest, Hungary.