The hepatitis C virus (HCV) can cause acute and chronic infections in humans. Worldwide, 71 million individuals are chronic carriers of HCV. Each year, nearly 700,000 people die due to the complications of this infection (cirrhosis and hepatocellular carcinoma).
The hepatitis C virus is transmitted by blood. Transmission is the result of exposure to infected blood, injectable drug use, medical care, and the transfusion of blood or derivatives not tested for HCV (all products are tested in France, where the risk of transfusion has disappeared). The risk of sexual transmission of HCV is extremely low among stable heterosexual couples, but high among men who have sex with men (MSM) using psychoactive substances for sexual intercourse ("chemsex") and those exposed to traumatic practices. The risk of mother-to-child transmission is very low. Venous drug use is now the main mode of HCV transmission. The prevalence of HCV among injectable drug users (IDU) is on average 70%. In France, it was 58% in 2004 and 43% in 2011. Transmission during invasive medical procedures is clearly decreasing due to a strengthening of general precautions against asepsis.
In France in 2011, the prevalence of antibodies against HCV was estimated to be 0.75%, and the prevalence of HCV RNA, which indicates an active infection, 0.42% (approximately 193,000 individuals with chronic infection). The incidence of acute hepatitis C in France is not known because there is no mandatory reporting system. In Europe, HCV infection is responsible for approximately 10% of cases of acute hepatitis. The diagnosis of acute hepatitis C is rare, except in certain exposed populations (MSM, IDU).
Incubation lasts two weeks to six months. Acute hepatitis C is asymptomatic in approximately 80% of infected individuals. The serum activity of alanine aminotransferase (ALT) is elevated in all cases. In 10 to 40% of subjects, the acute infection is limited and spontaneously resolves; only anti-HCV antibodies persist in the blood thereafter. The remaining patients develop a chronic infection.
Chronic hepatitis C is defined as the persistence of HCV RNA for more than six months after acute hepatitis. Chronic infection is responsible for chronic hepatitis, which usually progresses slowly in the absence of comorbidity factors (20 to 30 years on average) to cirrhosis or HCC. It is estimated that approximately 20 to 30% of patients with chronic hepatitis C will develop cirrhosis, HCC, or both over a 30-year period. The risk of cirrhosis and cancer increases with the duration of infection and is greater in individuals infected after the age of 40 and/or those who consume alcohol excessively. Extrahepatic manifestations can be observed during chronic hepatitis C. The most common is mixed cryoglobulinemia, which can cause cryoglobulinemic vasculitis associated with severe neurological, dermatological, and/or renal manifestations.
The diagnosis of HCV infection is based on the detection of anti-HCV antibodies in blood samples taken from the arm at the bend of the elbow. Anti-HCV antibodies can also be detected using rapid diagnostic orientation assays (TRODs) using capillary blood from a fingerstick or saliva. TRODs are particularly useful for reaching populations that do not have access to usual structural care. If anti-HCV antibodies are present, HCV RNA should be sought to demonstrate the presence of the virus as a sign of active infection. The persistence of HCV RNA beyond six months after acute hepatitis defines chronic HCV infection. Chronic hepatitis C is characterized by the simultaneous presence of antibodies to HCV and viral RNA in subjects with clinical and/or biological signs of chronic liver involvement.
The treatment of hepatitis C is undergoing a genuine revolution with cure rates of infection now close to 100%. There are four classes of molecule that are used as direct antivirals: protease inhibitors, NS5A protein inhibitors, nucleotide viral polymerase inhibitors, and non-nucleoside viral polymerase inhibitors. These molecules are used in combination, associating an NS5A inhibitor with one or two other molecules. These combinations are administered for 8 to 24 weeks. They are highly effective and very well-tolerated.
To date, there is no vaccine against HCV. In France, standard prevention strategies have reduced the incidence of HCV infection, except in certain populations, in particular MSM and prisoners. Combined (or multiple) prevention is now recommended, consisting of behavioral prevention methods, the widening of screening indications (systematic screening for men aged 18 to 60 and pregnant women from the first prenatal consultation), and initiating antiviral treatment at diagnosis to reduce transmission.