1. Institute for Medical Microbiology and Infection Control, University Hospital, Goethe University, Frankfurt, Germany
2. Electron Microscopy Facility, Max Planck Institute for Developmental Biology, Tübingen, Germany
3. Federal Institute for Vaccines and Biomedicines, Department of Virology, Paul-Ehrlich-Institut, Langen, Germany
4. Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway