Researchers in California conducted a cross-sectional study with 500 heterosexual, sexually active, monogamous couples in which one partner had chronic hepatitis C virus (HCV) infection. The researchers recruited these participants between 2000 and 2003. Participants were required to have been in a monogamous sexual relationship for at least three years and to be currently sexually active. Injecting drug users and persons with hepatitis B infection or HIV coinfection were excluded, as were couples with the HCV-infected partner taking antiviral drugs.
The participants with HCV and their partners received HCV antibody and viral load tests; participants with HCV also had genotype analysis, and for couples with concordant genotype infection, researchers conducted phylogenetic analysis to determine if the infections were genetically linked. Participants also provided information about sharing grooming and hygiene equipment. The couples had been together for a median of 15 years and had a median age of 48 years; approximately 75 percent of participants were white. The persons with HCV and their partners were interviewed separately about their sexual behavior. Approximately 17 percent of the couples used condoms in the first year of the relationship; this dropped to 13 percent in the year of the study. Participants also answered questions about sexual behavior that potentially involved contact with blood, as HCV is primarily a blood-borne virus.
The estimated incidence of sexual HCV transmission ranged from 3.6 per 100,000 person years, or 1 transmission per 380,000 sexual contacts, to a maximum of 7.2 per 100,000 person years, or 1 transmission every 190,000 sexual acts. The researchers concluded that sexual transmission of HCV among monogamous heterosexual couples is an extremely infrequent event. Since condom use was infrequent and decreased throughout the course of the sexual relationship, the low rate of sexual transmission was not due to use of barrier methods. The researchers could not pinpoint any sexual practices linked with increased risk of sexual transmission. However, couples with whom possible sexual transmission occurred were more likely to report vaginal sex during menses and anal sex than couples with no evidence of sexual transmission. They also reported less frequent condom use. The researchers noted that the outbreaks of sexually transmitted HCV reported in HIV-positive gay men in a number of countries likely resulted from “disrupted mucosal integrity” and the effects of HIV coinfection.
The full report, “Sexual Transmission of Hepatitis C Virus Among Monogamous Heterosexual Couples: The HCV Partners Study,” was published online in the journal Hepatology (2013; doi:10.1002/hep.26164).