What mode of transmission is most likely responsible for hepatitis C infection in a non-injecting drug user?

Hepatitis C is primarily spread through blood-to-blood contact. For non-injecting drug users, the sharing of a crack pipe is a mode of transmission that can involve blood exposure if the pipe is shared among users who have cuts or sores in their mouths or if blood-contaminated substances are present.

When individuals share smoking paraphernalia, the risk of transmitting infectious blood can occur if a user has an active infection that introduces the virus into the shared equipment. This is particularly significant for substances like crack cocaine, where the act of sharing involves the potential for blood exposure.

In contrast, sharing needles is directly associated with injecting drug use, and unprotected sexual contact, while a recognized route for hepatitis transmission, is significantly less common for hepatitis C compared to those methods associated with blood exposure. Blood transfusion is another mode of transmission, but the risks have been largely mitigated in many healthcare settings due to improved screening practices. Thus, in the context of non-injecting drug users, sharing a crack pipe emerges as a significant risk factor for hepatitis C infection.