What causes hepatitis C?

Updated: May 10, 2019
  • Author: Nicholas John Bennett, MBBCh, PhD, MA(Cantab), FAAP; Chief Editor: Russell W Steele, MD  more...
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Direct percutaneous exposure is the primary means of transmission. Blood transfusions are another means of transmission.

Historically, most hepatitis C virus infections result from blood transfusions. The risk of transfusion-borne hepatitis C virus began to decline in 1986, when surrogate-marker screening of blood donors started. Further declines were noted after the introduction of hepatitis C virus–directed antibody screening in 1990 (first generation) and 1992 (second generation). The current risk of transfusion-derived hepatitis C virus is estimated to be 1 case in every 100,000 units transfused.

Currently, the use of injected drugs is the most important epidemiologic risk factor, probably accounting for around 50% of both acute and chronic infections. Other parenteral routes may be involved.

Hemodialysis is a possible cause of hepatitis C virus infection. Health care employees may be accidentally exposed. Tattooing, body piercing, and acupuncture with unsterile equipment are possible routes of infection.

The risk of sexual transmission appears to be low, even among individuals with multiple sex partners. However, the presence of coexisting sexually transmitted diseases (eg, human immunodeficiency virus [HIV] infection) appears to increase the risk.

Vertical transmission may occur. Perinatal transmission is possible and affects an estimated 5% of babies born to mothers with hepatitis C virus infection. The risk is higher for babies born to mothers who are co-infected with hepatitis C virus and HIV or hepatitis B virus. [1]

Density of viral infection with hepatitis C virus affects the likelihood of transmission from mother to child in utero. While density of approximately 100 particles per milliliter produced no vertical transmission to the baby, 1 million particles per milliliter resulted in a transmission rate of 36%. [2] Overall, transmission to babies was 6% in mothers who were hepatitis C virus antibody–positive and 10% in mothers who were hepatitis C virus RNA–positive. Breastfeeding is not contraindicated for mothers with hepatitis C virus infection.

Approximately 10% of adults with hepatitis C virus infection have no identified risk factor for infection.

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