1. Department of Medical Microbiology and Immunology, University of Aarhus, Aarhus, Denmark
2. Abteilung Virologie, Institut fur Medizinische Mikrobiologie und Hygiene, Universität Freiburg, Freiburg, Germany
3. Department of Biochemistry, Trinity College, Dublin, Ireland
4. Department of Microbiology, National Public Health Institute, Helsinki, Finland