[Epidemiology of human diseases caused by unconventional transmissible agents].

Human unconventional viruses infections are scarcely found with a worldwide occurrence below 1/million inhabitants. The disease would be induced by an interaction between the patient's genetic characteristics and environmental factors. No link has been found between the occurrence of the disease in man and the presence of the animal form of the disease, i.e. scrapie. The professional risk has been pointed out for people working with animals or in the medical sector. Most iatrogenic cases are subsequent to a growth hormone treatment. The other cases are associated with different medical and surgical acts. But the transmission by blood transfusion remains questionable and must be clearly demonstrated.