Department of Biosystems Science and Engineering, ETH Zurich, 4058 Basel, Switzerland. SIB Swiss Institute of Bioinformatics, 4058 Basel, Switzerland. Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, 8091 Zurich, Switzerland. Institute of Medical Virology, University of Zurich, 8091 Zurich, Switzerland. Laboratory of Virology, University Hospital Geneva, 1205 Geneva, Switzerland. University Hospital Lausanne, Service of Immunology and Allergy, University Hospital Center, 1011 Lausanne, Switzerland. Molecular Virology, Department of Biomedicine-Petersplatz, University of Basel, 4009 Basel, Switzerland.