[Prions and risks for blood transfusion: the situation in 2003].

In 2003, Prions still constitute a biological enigma and a public health concern. The risks of transmission of the so called "mad cow disease" are now under control but concerns still persist about potential secondary transmissions, notably via blood transfusion. Information obtained from diseases previously observed in animals (scrapie of sheep and goat) and in man (Kuru, Creutzfeldt-Jakob disease) demonstrate the complexity of the relations between these transmissible agents and their host. The difficulty in decontamination, the very long silent incubation period during which diagnosis is not possible and the lack of treatment are alarming elements which explain the increased perception of risk for these diseases. The development of rapid screening tests used on bovine at slaughterhouse has represented an important improvement in the development of a targeted protection against these agents. Today, technical evolutions in diagnosis let us imagine the possibility of blood detection for prions: on one hand new garanties for security may arise but on the other hand it points out the potential infectivity of blood with these agents responsible for constant fatal diseases. Precautionary security measures have to ensure an optimal ratio benefit/risk for the patient and thus, in this field, to balance the risk linked to prions with those clearly identified elsewhere.