1. Viral Genetics Laboratory, Faculty of Sciences, Vrije Universiteit Brussel
2. Department of Molecular and Cellular Interactions, Flanders Institute for Biotechnology (VIB), Pleinlaan 2, B-1050 Brussels, Belgium
3. Fort Dodge Animal Health, 800 Fifth Street NW, Fort Dodge, Iowa 50501
4. Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium