Exposure of Hepatitis C Virus–Negative Recipients to ⩾2 Infected Blood Donors

This study analyzed 4 cases of hepatitis C virus (HCV)-naive transfusion recipients who developed hepatitis after receiving blood from >1 HCV-infected donor. One recipient was exposed to 4 donors, 2 were exposed to 3 donors, and 1 was exposed to 2 donors. For 3 recipients, the strain from 1 of the donors predominated in all follow-up samples collected for 8-40 months. For 2 recipients, the strain from the second donor was occasionally detectable with sensitive strain-specific assays. For the fourth recipient, the initially dominant strain was later supplanted by a strain from the other donor. Simultaneous exposure to multiple HCV strains may result in concomitant infection by >1 strain, although a single strain rapidly establishes its dominance. These observations are compatible with the presence of competition among infecting HCV strains that results in the dominance of 1 strain and competitive exclusion or suppression of other strains.