1. Department of Hematology, Oncology and Clinical Immunology, Heinrich-Heine University, 40225 Duesseldorf, Germany
2. Institute of Medical Microbiology and Hospital Hygiene, University Hospital Duesseldorf, 40225 Duesseldorf, Germany
3. Institute of Virology, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany