Hepatitis C Infections in the US in 2007, by Transmission Methods
"Of the cases reported in 2007 for which information concerning exposures during the incubation period was available, the most common risk factor identified was IDU (48%). During 1998–2007, IDU [intravenous drug use] was reported for an average of 44% of persons (range: 38%–54%). In 2007, 42% reported having multiple sex partners during the incubation period, 10% reported having sexual contact with another known HCV-infected person, and 10% were MSM [men who have sex with men]. Having had surgery was reported for 20% of persons with hepatitis C; the percentage was higher for persons aged >40 years (32%). A total of 2% reported occupational exposure to blood."
Centers for Disease Control and Prevention, "Surveillance for Acute Viral Hepatitis -- United States, 2007," Surveillance Summaries, May 22, 2009, MMWR 2009;58(No. SS-3), p. 6.