1 Department of Infectious Diseases, Molecular Virology, University Hospital Heidelberg, Im Neuenheimer Feld 345, D-69120 Heidelberg, Germany; German Center of Infectious Diseases (DZIF), Heidelberg, Germany.
2 Department of Infectious Diseases, Molecular Virology, University Hospital Heidelberg, Im Neuenheimer Feld 345, D-69120 Heidelberg, Germany; German Center of Infectious Diseases (DZIF), Heidelberg, Germany. Electronic address: Stephan.Urban@med.uni-heidelberg.de.