Blood exposure for the most part, some sexual contact, esp in men who have sex with men (PubMed). And amateur tattoos (PubMed). Avoid amateur tats, but those who get their friends to do the tats probably are not particularly fastidious in the first place (PubMed).
The sex, drugs and rock 'n' roll have caught up with boomers (born between 1945 and 1965; wait, that includes me). The CDC suggests all boomers be tested for Hepatitis C.
The incidence of HCV transmission among couples was 3.6 per 10,000 person-years with an estimated risk per sexual encounter of 1 per 380,000 (PubMed).
ICD9 Codes (Soon to be supplanted by ICD10)
Hepatitis C 070.51.