HEPATITIS C

Epidemiology

Hepatitis C virus (HCV) is endemic in most areas of the world, with approximately 3% (170 million) of the world's population infected. 

HCV prevalence is highest (17% to 26%) in Egypt, Tibet, Bolivia, Cameroon and Guinea.

HCV prevalence is intermediate (1% to 5%) in eastern Europe, the Mediterranean, the Middle East, the Indian subcontinent, parts of Africa, and Asia.

HCV prevalence is low (0.2% to 0.5%) in western Europe; North America; most areas of Central America; Australia; and limited regions of Africa, including South Africa.

HCV prevalence is lowest (0.01% to 0.10%) in the United Kingdom and Scandinavia.

Cause or causative agents

            Hepatitis C is a liver disease caused by the hepatitis C virus, an enveloped RNA virus in the flaviviridae family (similar to the yellow fever and dengue viruses), which is found in the blood of infected people. 

Transmission

          The virus is acquired through person-to-person transmission by parenteral routes. The incubation period is 7-8 weeks. Before screening for HCV became available, infection was mainly transmitted by transfusion of contaminated blood or blood products. Nowadays transmission frequently occurs through use of contaminated needles, syringes and other instruments used for injections and other skin-piercing procedures. Sexual or perinatal transmission of hepatitis C occurs rarely. There is no insect vector or animal reservoir for HCV.

Risk to the traveller

            Travellers are at risk if they practice unsafe behaviour involving the use of contaminated needles or syringes for injection, acupuncture, piercing or tattooing. An accident or medical emergency requiring blood transfusion may result in infection if the blood has not been screened for HCV. Travellers engaged in humanitarian relief activities may be exposed to infected blood or other body fluids in health care settings.

Signs and symptoms

            Most (60-70%) HCV infections are asymptomatic. In cases where infection leads to clinical hepatitis the onset of symptoms is usually gradual with anorexia, fatigue, abdominal discomfort, nausea and vomiting, followed by the development of jaundice in some cases (less commonly than in hepatitis B). Most clinically affected patients will develop a long-lasting chronic infection with waxing and waning aminotransferase levels.

            Because the disease progresses slowly in the body, symptoms can appear 20 - 30 years after the initial infection. 

Secondary or associated medical condition

About 80% of newly infected patients progress to develop chronic infection. Cirrhosis develops in about 10% to 20% of persons with chronic infection, and liver cancer develops in 1% to 5% of persons with chronic infection over a period of 20 to 30 years. Most patients suffering from liver cancer who do not have hepatitis B virus infection have evidence of HCV infection. The mechanisms by which HCV infection leads to liver cancer are still unclear. Hepatitis C also exacerbates the severity of underlying liver disease when it coexists with other hepatic conditions. In particular, liver disease progresses more rapidly among persons with alcoholic liver disease and HCV infection.

Diagnosis

Diagnostic tests for HCV are used to prevent infection through screening of donor blood and plasma, to establish the clinical diagnosis and to make better decisions regarding medical management of a patient. Diagnostic tests commercially available today are based on enzyme immunosorbant assays (EIA) for the detection of HCV specific antibodies (anti-HCV). EIAs can detect more than 95% of chronically infected patients but can detect only 50% to 70% of acute infections. A recombinant immunoblot assay (RIBA) that identifies antibodies which react with individual HCV antigens is often used as a supplemental test for confirmation of a positive EIA result.

Testing for HCV circulating by amplification tests RNA (e.g. polymerase chain reaction or PCR, branched DNA assay) is also being utilized for confirmation of serological results as well as for assessing the effectiveness of antiviral therapy. A positive result indicates the presence of active infection and a potential for spread of the infection and or/the development of chronic liver disease.

Treatment

Antiviral drugs such as interferon taken alone or in combination with ribavirin can be used for the treatment of persons with chronic hepatitis C, but the cost of treatment is very high. Therapy should be considered in patients with aminotransferase elevations, biopsy evidence of moderate or severe chronic hepatitis and/or HCV RNA in the serum.  Treatment with interferon alone is effective in about 10% to 20% of patients. Interferon combined with ribavirin is effective in about 30% to 50% of patients. Ribavirin does not appear to be effective when used alone. However 50% of patients relapse within 12 months of treatment.  Sustained response is associated with loss of HCV RNA from serum.  The benefit of treatment in patients with normal or nearly normal serum aminotransferase levels or decompensated cirrhosis is doubtful.

Prevention

There is no vaccine against HCV. Research is in progress but the high mutability of the HCV genome complicates vaccine development. Lack of knowledge of any protective immune response following HCV infection also impedes vaccine research. It is not known whether the immune system is able to eliminate the virus. Some studies, however, have shown the presence of virus–neutralizing antibodies in patients with HCV infection.

In the absence of a vaccine, all precautions to prevent infection must be taken including:

·        Screening and testing of blood and organ donors;

·        Virus inactivation of plasma derived products;

·        Implementation and maintenance of infection control practices in health care settings, including appropriate sterilization of medical and dental equipment;

·        Promotion of behaviour change among the general public and health care workers to reduce overuse of injections and to use safe injection practices; and risk reduction counselling for persons with high-risk drug and sexual practices.

References

WHO International Travel & Health, 2002

WHO Fact Sheet WHO/164  revised Oct 2000

Health Canada About Hepatitis C, 2002/03/30, modified: 2002/08/06

CDC  Health Information for International Travel 2001-2002  Hepatitis, Viral, Type C, reviewed Feb 25, 2002

Harrison’s Manual of Medicine, 15/E for PDA, The McGraw-Hill companies, 2003