Epidemiology of HCV infection in the general population and in blood transfusion.

The prevalence of HCV seropositivity observed in various populations raise the issue of the contamination routes and the corollary exclusion criteria of risk subjects from blood donation. There are various diagnostic methods for HCV infection. The biological diagnosis is reached at three levels: circulating antibody screening by second and third generation tests; screening validation by immunoblot, to distinguish between the various HCV specific antibodies and detection of viral nucleic acids by molecular biology. In blood donors in France, 0.5% were seropositive in 1990, 0.3% in 1992 and 0.1% (essentially new donors) in 1995. This decrease is the result of improved test specificity and sensitivity and donor selection. In Europe, prevalences range from 0.1-1.5% with a North-South gradient. In other countries: 0.3% in Canada, 0.6% in the USA, 1-2% in China, Thailand and Japan, from 0.2% to 20% in Africa. In risk populations contamination by blood is manifest: HCV seropositivity in 80% of drug abusers, 10-60% of dialysis patients before 1991, more than 80% of haemophiliacs treated before 1986, 10% of labile blood product recipients before 1988. The nosocomial transmission figures are even worse: 2-5% of hospitalized patients are thought to be contaminated. Perinatal and sexual contaminations are not excluded (3-30%) and they vary according to the degree of exposure and the viral type of post-transfusional HCV infection: prevention implies several types of action: information and education of populations about risk factors; medical interview before each blood donation; systematic serological testing; manufacturing measures for stable (SD processing) and labile (deleukocytation, plasma seroattenuation) blood products; prescription recommendations and follow-up measures; haemovigilance (clinical and biological follow-up of all recipients of human blood products).