A population of hematological cancer patients as recipients of many blood components and that of donors of blood components and bone marrow are related to the common event of contamination with viruses of blood-borne infections, which occurs and is detectable during long-term treatment and follow-up. They share interaction traits and diverse communication mechanisms, which call for complex interrelated trials in both groups with a mandatory epidemiological evidenced-based investigation of all cases of posttransfusion hepatitis B and/or C. The identity of infection with hepatitis B and C viruses, human immunodeficiency virus, and their association should be simultaneously studied in the populations of both donors and recipients of blood components and bone marrow.