[Hepatitis virus C: from discovery to applications in public health].

After 15 years of unsuccessful efforts, the most frequent of hepatitis non-A non-B viruses has just been identified and called hepatitis C virus (HCV). The viral genome had been sequenced by an original and direct molecular biology method before the agent could be detected serologically or at electron microscopy. HCV is a small, encapsulated RNA virus, perhaps loosely related to flaviviruses. A non-structural protein, corresponding to the virus replication enzyme, is the specific component as target for ELISA tests to detect specific anti-HCV antibodies. This serology has enabled us to confirm that HCV is the most common of NANB viruses, being responsible for 60 to 80 p. 100 of all cases of post-transfusion hepatitis. The antibodies appear belatedly: in 40 p. 100 of patients they do so during convalescence, 2 to 12 months after the serum transaminase peak of primary infection. 60 to 80 p. 100 of patients with presumed NANB hepatitis are positive for anti-HCV antibodies. The same applies to cirrhosis and cancer which, in 40 p. 100 of the cases, complicates post-NB hepatitis cirrhosis. Since March 1, 1990, screening for anti-HCV antibodies has become compulsory for all blood donors in France. The prevalence of these antibodies is 0.68. Among groups of patients at risk, prevalences are 70 p. 100 in haemophiliacs, 50-75 p. 100 in drug addicts and more than 30 p. 100 in patients under haemodialysis. Sexual transmission seems to be weak but possible; 5 p. 100 of homosexuals carry anti-HCV antibodies, and this percentage is higher in HIV positive subjects. The discovery of the hepatitis C virus coincides with the finding that interferon is effective in the treatment of NANB hepatitis, and this exceptional opportunity in the field of public health should engender specific programmes. It may now be hoped that prevention by vaccine will be available in a not too distant future.