1. Institute for Zoo Biology and Wildlife Research; Alfred- Kowalke-Strasse 17 D-10315 Berlin Germany
2. Medical Institute of Environmental Hygiene; Heinrich-Heine-University; Auf'm Hennekamp 50 D-40225 Dusseldorf Germany
3. Tierpark Berlin-Friedrichsfelde; Am Tierpark 125 D-10307 Berlin Germany
4. Institute of Microbiology, German Armed Forces Medical Academy; Neuherbergstrasse 11 D-80937 Munich Germany
5. WHO Collaborating Centre for Collection and Evaluation of Data on Comparative Virology, Veterinary Faculty; Veterinaerstrasse 13 D-80539 Munich Germany
6. Institute of Medical Microbiology, Infectious and Epidemic Diseases, Ludwig Maximilians University; Veterinaerstrasse 13 D-80539 Munich Germany