A high human immunodeficiency virus (HIV) load may increase the probability
of HIV transmission by sexual contact, but the association of virus load o
f hepatitis C virus (HCV) with risk of HCV transmission is uncertain. HIV a
nd HCV virus loads were examined in hemophilic men, as were risks of HIV an
d HCV transmission to their female partners in a hemophilia cohort in which
most subjects are dually infected. A higher HIV load was associated with a
n increased risk of HIV transmission (odds ratio [OR], 1.31 per log(10) inc
rease in virus load). A higher HCV load was associated, although not signif
icantly, with an increased risk of HCV transmission (OR, 1.42 per log(10)).
HCV load was higher among dually infected men than in those infected with
HCV alone (P = .001). However, much larger studies are needed to clearly sh
ow whether HIV/HCV coinfection significantly increases the risk of HCV tran
smission to female partners.