The most common chronic blood-borne infection in the United States is caused by hepatitis C virus (HCV), an RNA virus transmitted through blood-to-blood contact.1 Approximately 4 million Americans are currently infected.1-3 During the 1980s, as many as 230,000 new HCV infections were diagnosed each year.4 The development of antibody testing for HCV and routine screening of blood donations reduced this figure to about 25,000 new infections per year by 2001.4
However, the large burden of disease from the earlier years remains, and the morbidity and mortality associated with HCV are expected to increase over the next 2 decades.5 HCV-associated end-stage liver disease is the most frequent indication for liver transplantation in the western world.6
In this article, we identify risk factors for HCV infection and discuss which patients should be tested and treated.
In the past, the 2 most important modes of viral transmission weretransfusion of infected blood products and sharing of contaminated needles by injection drug users.4 Injection drug use accounts for about 60% of all new cases of hepatitis C in the United States.4 However, since 1992, when blood screening for HCV was introduced, the risk of contracting hepatitis C from a transfusion has been reduced to approximately 1 in 1.18 million donations.7 Patients who received transfusions before July 1992 remain at risk. Persons with hemophilia run a substantially higher risk: nearly 90% of patients who received factors made before 1987 have been infected with HCV.4,8 Rigorous screening and viral inactivation procedures have virtually eliminated this mode of transmission.
Nosocomial transmission of HCV in the United States is relatively rare. Nevertheless, all health care personnel should be aware of the risks and should strictly observe universal precautions. At present, the rate of HCV infection among hospital workers (including surgeons) in the United States is similar to that in the general population, averaging 1% to 2%.4 Needlestick and sharps-related injuries remain a source of HCV infection. However, the incidence of HCV seroconversion after an incident is only about 1.8%.4 Moreover, the risk of transmission from infected health care workers to patients appears to be very low; only isolated cases have been reported.4
The risk of nosocomial transmission is highest in the hemodialysis unit, where the prevalence of HCV infection among patients undergoing long-term hemodialysis is 8.4% and among unit workers, 1.7%.9 Inadequate infection control has been cited as the most likely explanation for the increased prevalence in these units. However, there is no difference in the prevalence of the antibody against HCV (anti-HCV) at centers that reuse dialyzers on anti-HCV-positive patients compared with those that do not reuse dialyzers. Medical personnel in hemodialysis units should use gloves whenever they touch patients or equipment and should never allow patients to share instruments or medications.4
Although sexual contact is one of the most common modes of transmission for hepatitis B virus infection, HCV appears to be transmitted less readily via this route. A recent study showed no transmission of HCV during a 3-year follow-up of 600 spouses of patients with chronic hepatitis C.6 The CDC does not recommend any changes in sexual practices in long-term monogamous relationships in which one of the part- ners is infected with HCV.
Vertical transmission from HCV-positive mothers is also an important mode of disease transmission. Women infected with HCV have approximately a 5% to 6% risk of transmitting the virus to their infants. For infants born to women coinfected with HCV and HIV, the rate of HCV transmission is 14% from anti-HCV-positive mothers and 17% in mothers with documented HCV viremia.4,10 Many studies have shown a failure of HCV transmission through breast-feeding, which has led to the assumption that this practice is safe in HCV-infected mothers.11-13 However, the same cannot be said for those coinfected with HCV and HIV.
Less common modes of transmission include percutaneous exposure through tattooing and body piercing, and through the sharing of razor blades, toothbrushes, pedicure and manicure items, and other objects that might be exposed to blood.4 One study has suggested that HCV infection may also be transmitted via shared straws used in cocaine inhalation.14 However, the significance and extent of these modes of transmission remain unclear.
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