Injection drug users (IDUs), if they share needles with other people, are at the highest risk of HCV.
To cause a new infection, HCV must pass from the blood of an infected person into the blood of an uninfected (susceptible) person. In other words, HCV is most easily spread through direct blood-to-blood contact, such as:
Sharing needles and other equipment (paraphernalia) used to inject drugs.
Needle-stick injuries and exposure of open wounds or mucous membranes to infected blood. (Note: The risk to health workers is actually quite low—4 to 10 percent risk through a needle-stick injury involving a needle previously used in someone infected with HCV.)
Blood or blood-product transfusion (especially before 1992).
Unlike human immunodeficiency virus (HIV), which causes AIDS, it is generally believed that HCV cannot be transmitted through semen or other genital fluids, unless blood is present. Thus, the risk of becoming infected with HCV through unprotected sexual intercourse is low—but it is still possible. As a result, experts recommend that people infected with HCV practice safer sex using a protective barrier (e.g., condoms), especially during intercourse, as a precaution for their partners.
Women who are infected with HCV have a less than 10 percent chance of passing the virus along to their babies during pregnancy or delivery, although the risk increases if the woman’s HCV viral load (the amount of HCV in a measurement of blood) is high. It is unlikely that HCV can be transmitted through breast feeding or breast milk.
You may be at risk for hepatitis C and should contact your health care provider for a blood test if you:
Were notified that you received blood from a donor who later tested positive for hepatitis C
Have ever injected illegal drugs, even if you experimented a few times many years ago
Have ever gotten a tattoo or piercing in a no-professional setting where equipment such as ink, inkwells or needles are resused and potentially unsterilized.
Received a blood transfusion or solid-organ transplant before July 1992
Received a blood product for clotting problems before 1987
Have ever been on long-term kidney dialysis
Have evidence of liver disease (e.g., persistently abnormal liver function tests)
Have had multiple sexual partners, or sexual contact with an HCV-positive person