IV drug users represent the largest single risk group. Hepatitis C infection among intravenous drug users occurs at an alarming rate. As with HIV, the sharing of contaminated needles and syringes increases the chance of infection dramatically: incidence of HCV antibody rates among I.V. drug users has surpassed 50 percent in many studies and almost reached 100 percent in others. Within only six months to a year after beginning intravenous drug use, 50-80 percent of drug users test positive for the hepatitis C antibody. I.V. drug users account for about 30-40% of all identified cases, and about 50 percent of all new cases of the disease.
Sexual contact has been clearly identified as a means of transmitting hepatitis C. Several studies of risk factors in sexual activity found rates of infection between 1 and 18% for homosexually active individuals, 1 to 10% among heterosexually active individuals, and 1 to 12% among female prostitutes, with the primary risk factors for infection being greater numbers of partners, unprotected sex, simultaneous infection with other STD's, and traumatic sexual activity. Seroprevalence for long term partners of hepatitis C patients was found to be around 5%.
Household contact with another household member that has hepatitis
C has also been strongly implicated, and this, in combination with heterosexual exposure, is believed to be responsible for approximately 13% of all infections. The incidence of household-member transmission cases has more than doubled since 1990. Maternal-infant transmission has also been documented as a mode of spread, occuring in no more than six percent of children of hepatitis C positive mothers.
Around 2% of all cases of hepatitis C are thought to be contracted through the occupational risk (needle-stick injuries, blood spills, etc) involved with the health care profession.
