Hepatitis C is a parenterally transmitted viral liver disease which used to be described as "non A, non B" hepatitis until the causative agent was discovered in 1989. The discovery and characterisation of the virus, since then called the hepatitis C virus or HCV, allows us to understand the essential role it plays in post-transfusion hepatitis and the reason why it tends to cause persistent infection.
HCV is a major cause of acute hepatitis and chronic liver disease, particularly cirrhosis and liver cancer. It is estimated that 170 million people throughout the world are chronic carriers of HCV, and that 3 to 4 million people are infected each year. HCV is mostly transmitted by direct contact with human blood. The main routes of transmission throughout the world are transfusion of blood which has not been screened, and the re-use of non-sterile syringes and needles.
At present there is no vaccine against hepatitis C. Treatment of the chronic disease is too expensive for most patients in developing countries. Therefore, the most effective way to combat hepatitis C is probably to reduce the risk of nosocomial HCV transmission (blood transfusions, risky injections, etc.) and risky behaviour, such as the use of injectable drugs.
The pathogenic agent
HCV is one of five viruses (A, B, C, D, and E) that together are responsible for the large majority of cases of viral hepatitis. It is an enveloped RNA virus belonging to the Flaviviridae family, and has a limited range of hosts. The only species sensitive to infection appear to be human beings and chimpanzees, the disease being similar in both. A potentially important feature of the virus is the relatively large capacity of its genome to mutate, which is probably related to the large propensity of the virus to cause chronic infections in 80% of cases. HCV has several different genotypes which play an important role in the severity of the disease and its response to treatment.
Clinical features of acute infection
The incubation period for HCV infections before clinical symptoms appear is 15 to 150 days. The most common symptoms in acute infection are fatigue and jaundice. However, the infection is asymptomatic in the great majority of cases (between 60 and 70%) even in the chronic phase.
Chronic infection and its consequences
The infection becomes chronic in approximately 80% of newly infected patients. Between 10 and 20% of chronic carriers develop cirrhosis, 1 to 5% of whom in turn develop liver cancer after 20 to 30 years. Traces of HCV infection are found in most patients with liver cancer who do not have hepatitis B. The mechanism by which hepatitis C leads to liver cancer has not been established yet. Hepatitis C also aggravates any pre-existing liver disease to which it is added. Liver cancer therefore progresses faster in people who have alcoholic hepatitis and who are also HCV carriers.
Methods of transmission
HCV is mainly transmitted by direct contact with human blood. It has been clearly demonstrated that infection may occur during transfusion of blood which has not been tested for the hepatitis C virus if needles, syringes, or any other poorly sterilised medical equipment has been reused or when syringes have been shared between users of injectable drugs. Perinatal or sexual transmission may also occur, although these cases are less frequent.
There are other routes of transmission which may be significant. For example, if the equipment used has not been correctly sterilised during certain social or cultural practices or certain behaviours involving a break in the skin (for example, piercing earlobes or other parts of the body, circumcision or tattooing).
HCV is not transmitted by sneezing , hugging, coughing, water, food, or shared use of dishes or from ordinary social contact.
In both developing and developed countries, the high risk groups are injectable drug users, transfusion patients, haemophilia patients, patients on dialysis, and those who have unprotected sexual intercourse with multiple partners.
It is estimated that 90% of chronic carriers of the virus in developed countries are or were injectable drug users, or have been transfused with untested blood or blood products.
The major methods of transmission involve using non-sterile injection equipment and transfusion of infected blood. In addition, people who perform traditional scarification and circumcision are at risk if they use or re-use instruments for this purpose which have not been sterilised.