[Epidemiology of infections linked to hepatitis C virus in France].

In France, the population of adult carriers of anti-HCV antibodies has been estimated about 600,000, but only 10 to 15% are aware of the diagnosis. Two major sources of infection have been identified : transfusion and intravenous drug use, accounting for 60% of HCV infections. In contrast, sexual or household transmission, mother-to-infant transmission or occupational exposure account for a small part of the HCV epidemic. In about 15% of cases, a nosocomial exposure is questioned, probably related to an insufficient decontamination of medical devices. Finally, no source of infection can be recognized in about 20% of infected patients. Among them, many have spent a long stay in high HCV prevalence areas, suggesting local percutaneous exposures. The diagnosis of chronic hepatitis C is often made late in the course of the disease, an average of 10 years after exposure. At this time, a cirrhosis is present in about 20% of the patients. The frequency of cirrhosis depends on the duration of the HCV infection, and probably also on the source of transmission, independently of the duration of the disease. Thus, it has been observed that cirrhosis was more frequent in transfusion recipients than in intravenous drug users. Such a difference could be related to different HCV genotypes in the different groups at risk. The genotype 1b has been found predominant in transfusion recipients whereas genotype 3a was more frequent in drug users. Recently, a slight modification in the relative frequency of the different genotypes, mainly spreading and increased frequency of genotype 3a could lead to a modified epidemiology of HCV infection. The consequences of such modifications need to be evaluated.