Det nedsatte immunforsvar kan enten skyldes, at patienten har blodkræft eller knogle - marvskræft og har fået kemoterapi, eller at patienten har fået en transplantation af bloddannende stam - celler (hæmatopoietisk stamcelletransplantation) og får høje doser af immundæmpende medicin.
This can be either because they have cancer in the blood or bone marrow and have received chemotherapy, or because they have had a haematopoietic stem cell transplant (a transplant of cells that make blood cells) and are receiving high doses of immunosuppressant medicines.