[Transfusion safety: emergent or hypothetical risks].

Three categories of emerging risks are studied: 1) A new variant of Creutzfeld-Jakob disease, different from its sporadic form; limited to the British isles (48 of 51 cases), it affects younger patients, and has a higher duration with a predominance of psychiatric symptoms. Environmental risk factors include a previous stay in the British isles and oral transmission via contaminated food. No link has been made evident between blood component (BC) transfusion and occurrence of the disease. A potential risk exists if its agent is found in blood and peripheral lymphoid tissues and if buffy coat from infected animals has been inoculated intracerebrally. Since 1993, prevention measures have been taken: exclusion of donors with a potential risk as well as transfused donors, systematic leukocyte reduction and implementation of disease surveillance. Excluding donors after a several month-stay in the British Isles is being discussed. 2) Novel hepatitis viruses. Hepatitis G virus (HGV) has been detected in 2-4% of blood donors. Ten percent of patients with chronic non-A-E hepatitis are HGV RNA positive. The incidence of HGV infection is higher than expected from PCR studies. HGV has a high prevalence in the world. Novel DNA non-enveloped virus (TTV) has a normal distribution. Its prevalence varies from 2 to 80%, depending on the country. Although it has not been shown to be aggressive for the liver, prolonged follow-up is required. 3) Human herpes virus 8 (HHV8) is associated with Kaposi's sarcoma in 80% of cases. Its prevalence (0-20%) varies depending on the country. Kaposi's sarcoma has never been reported after BC transfusion. PCR-based viral DNA searches have yielded negative results in 19 poly-transfused subjects. Continuous monitoring is required for recipients at risk (e.g., immunosuppressed). In response to a possible health risk, emerging risks govern the "Precaution Principle", so difficult to implement.