Hepatitis C virus (HCV)
Post-transfusion infectious hepatitis caused by agents other than hepatitis B has long been recognised. These cases, at one time, were collectively termed 'non-A non-B hepatitis', and the main cause is now known to be the hepatitis C virus (HCV). HCV has a worldwide prevalence, although rates of infection vary, depending on socio-economic factors, such as intravenous drug use and medical practices because it is primarily transmitted via direct introduction of the virus into the blood. It is estimated that 0.5-1 % of the UK population has a chronic HCV infection.
Pathogenesis of hepatitis C infection
Once inside the host, the HCV is transported in the blood to the liver, where it infects liver cells, although other types of cell, including blood cells, may also be infected. The incubation period for acute HCV infection is usually around 70 days, but can range from 2 to 26 weeks. The acute phase of HCV infection is often without symptoms, or mild. Diagnosis of infection is by detection of antibodies or virus RNA (ribonucleic acid) and/or antigen in serum. If the infection proceeds to a chronic phase, progression of liver damage is usually slow, and the most common complaint is fatigue. Liver enzyme abnormalities may fluctuate or persist, and the degree of liver damage is variable. The Department of Health estimates that between 60 to 80% of patients with acute HCV infection go on to develop chronic infection with a variable degree of hepatitis, with the risk of cirrhosis and, in a smaller number, primary liver cancer several decades later.
Further reading on the relationships between detectable HCV, antibody generation and the progression of disease:
Transmission of hepatitis C
Routine screening of blood donors has been introduced to prevent transmission via transfusion and the use of blood products. The greatest risk of acquiring HCV in the UK is now through sharing of blood-contaminated needles and injecting equipment among drug users.
Routine screening of blood donors has been introduced to prevent transmission via transfusion and the use of blood products. The greatest risk of acquiring hepatitis C (HCV) in the UK is now through sharing of blood-contaminated needles and injecting equipment among drug users. Workplace exposure in the healthcare setting usually occurs as a result of a needle-stick or injury with other contaminated sharp instruments, and rates of occupational exposure and transmission are presented in HPA's Eye of the Needle report. Exposure to other contaminated sharp injuries, for instance, via tattooing and skin piercing, may also result in infection. Mother-to-baby transmission occurs at a rate of about 3-5% (up to 15% in mothers who are also infected with human immunodeficiency viruses (HIV).
Prevalence of the hepatitis C virus (HCV) in the UK
HCV infection is a major worldwide public health problem, although the UK is thought to be a low prevalence area. Based on seroprevalent studies performed on residual specimens, the prevalence of HCV in England is predicted to be around 0.5-1%. As with HIV infection, the prevalence of HCV is often higher in major cities or other highly populated regions, compared to other parts of the UK, and is mostly associated with high-risk groups. This is demonstrated by the high incidence of hepatitis C among injecting drug users in Glasgow, London and the North West of England, (See - Shooting Up: Infections among injecting drug users in the UK, 2007 (updated 2008)). Recent mathematical modelling data cited by the Health Protection Agency (HPA) indicates that, within England and Wales, 191 000 individuals had antibodies to hepatitis C virus. HPA also report 12 000 chronically infected individuals in Wales. In Scotland, (2006), around 50 000 people were estimated to be infected with hepatitis C; 38,000 with chronic infection. Estimates from Northern Ireland suggest that around 4000 individuals are likely to be chronically infected.
Most infections are due to injecting drug use. Since the discovery of HIV , there has been raised awareness of the transmission of blood-borne viruses through shared injecting equipment. However, a significant number of chronic infections may have been acquired in the 1970s and 1980s through contaminated blood products, before routine screening was introduced.
Approximately 80% of acute infections are without symptoms and 55-85% of all HCV infections become chronic. Therefore, it is likely that many infected individuals are unaware of their status. Some patients infected with HCV may also be infected with HIV or HBV (hepatitis B virus). Hepatitis C can now be treated. Around 50% of those who receive treatment clear the infection. As HCV infection is not always symptomatic, it is important that those at risk volunteer to be confidentially tested in order to benefit from such treatment. All blood donations are now tested for HCV. Again, the prevalence of HCV infection is likely to be higher in some areas and in some population groups, than in others.