[1] Univ Heidelberg, Dept Internal Med 5, D-69115 Heidelberg, Germany
[2] Univ Leipzig, Dept Haematol, D-7010 Leipzig, Germany
[3] Univ Heidelberg, Inst Hyg, D-69115 Heidelberg, Germany
[4] Univ Dusseldorf, Dept Haematol Oncol & Clin Immunol, D-4000 Dusseldorf, Germany