Hepatitis C

Causative agents

Hepatitis C is caused by the Hepatitis C virus. Hepatitis C is a hepacivirus made up of six genotypes. Hepatitis C virus is single stranded RNA virus.

Statistics

Approximately 170 million people are infected with HCV worldwide with between 3 to 4 million new infections each year.  Approximately 80% of infections become chronic.  Of these, liver disease develops in 10 to 20% and liver cancer in 1 to 5% after a period of 20 to 30 years.  It worsens existing liver disease.  While some newly infected individuals experience symptoms, the vast majority (60 to 70% are asymptomatic).  Treatment is effective in 10 to 50% of individuals, depending on the combination of therapies employed.[1]

Modes of Transmission

Transmission is primarily from contact with infected blood, such as through blood transfusions or contaminated needles.  Sexual and perinatal transmission has been documented but is less common.  Since there is no vaccine and treatment is costly, the best approach in developing countries is to prevent transmission through education and adequate screening of blood transfusions.[1]

Methods of diagnosis

The primary method of diagnosis is through the use of enzyme immunosorbant assays detecting the presence of antibodies specific for HCV.  This method detects more than 95% of chronic infections but only 50 to 70% of acute infections.  RIBA (recombinant immunoblot assay) is used as a supplement to confirm infection.  Real-time PCR testing is used to identify window period infections and to monitor response to antiviral therapies.[1]

Failures or shortcomings in different diagnostic strategies

HCV has an unusually long window period and consequently NAT provides significant reductions in the window period.  The window period reduction resulting from implementation of NAT is 63 and 46 days when compared to second and third generation antibody tests respectively.[2]

Annotated Bibliography

1. Anonymous, Hepatitis C Fact Sheet No. 164. 2000, World Health Organization.

2. Tobler, L.H., et al., Impact of HCV 3.0 EIA relative to HCV 2.0 EIA on blood-donor screening. Transfusion, 2003. 43(10): p. 1452-9.