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Hepatitis C

Hepatitis C virus (HCV) is a single-stranded RNA virus that is parenterally transmitted and is a major cause of chronic hepatitis and cirrhosis. The HCV genome has been completely sequenced, and the virus has recently been cultured and fully characterised.

Past or current infection with HCV can be identified by testing for the HCV antibody (anti-HCV). The currently used antibody tests are highly sensitive and specific for the diagnosis of hepatitis C. The number of false positives with these newer assays is very small. However, in acute HCV infection the anti-HCV test may take 2-3 months to become positive and an accurate diagnosis may require testing for HCV RNA by PCR.

Screening of healthy blood donors in Australia using current tests shows a viral carrier rate of about 0.3% among apparent healthy new blood donors. However, the prevalence in the population at large is thought to be approximately 1%, because assessment of potential blood donors screens out many people at increased risk of HCV infection. In particular, the likelihood of having HCV infection is substantially increased if a person has used illicit injecting drugs. The cumulative risk increases with duration of injecting drug use. The risk among “ever-users� of injecting drugs is 70%, and over 90% in those who have been using injecting drugs for more than two years at any stage of their life. Anybody who has ever used illicit injecting drugs, even once, has a 20-fold increased risk, over the general population, of having HCV.

The risk of acquiring HCV from a blood transfusion has declined exponentially since the screening of blood for HCV in Australia began in 1990. Screening has improved in accuracy, and the current risk of acquiring HCV from a single unit of transfused blood is extremely low.