1. Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Greenport, New York 11944
2. Southeast Poultry Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Athens, Georgia 30605
3. Department of Pathobiology and Veterinary Science
4. Center of Excellence for Vaccine Research, University of Connecticut, Storrs, Connecticut 06269
5. Area of Virology, School of Veterinary Sciences, University of Buenos Aires, Buenos Aires, Argentina
6. Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, Illinois 61802
7. Animal Production and Health Section, Joint FAO/IAEA, Division of Nuclear Techniques in Food and Agriculture, IAEA, Vienna, Austria
8. Department of Applied Biotechnology, Onderstepoort Veterinary Institute, P/Bag X5, Onderstepoort 0110, South Africa