1. Department of Infectious Diseases, Robert Koch-Institute, 13353 Berlin, Germany
2. Viral Vaccine Preventable Diseases Branch, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
3. Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison WI 53706, USA
4. Department of Infection and Immunity, Luxembourg Institute of Health, L-4354 Esch-sur-Alzette, Luxembourg
5. Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, 17493 Greifswald-Insel Riems, Germany
6. Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institute, 17493 Greifswald-Insel Riems, Germany