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Hepatitis C Sexual Transmission Is Rare among Monogamous Heterosexual Couples

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Transmission of hepatitis C virus (HCV) between long-term, monogamous, heterosexual partners can potentially occur, but appears to be very uncommon, according to a study of 500 couples described in the November 23, 2012, advance online edition of Hepatology. Furthermore, the analysis failed to find a link between HCV transmission and any specific sexual activities.

Prior studies of HCV sexual transmission have produced mixed results. Research generally has shown that transmission is rare -- estimated at 0%-5% -- between partners in stable heterosexual couples. The risk is higher for people with multiple sex partners, however, and outbreaks of presumed sexually transmitted hepatitis C have been reported among HIV positive urban gay men in Europe, Australia, and the U.S. during the past decade.

Norah Terrault from the University of California at San Francisco and colleagues conducted a cross-sectional (single time point) study of people with hepatitis C and their steady partners to estimate the risk for HCV infection among monogamous heterosexual couples.

"While it is generally agreed that the risk for transmitting HCV to sex partners is very low, the lack of quantifiable data has been a limitation to clinicians counseling their patients," the study authors wrote. "Thus, the major objectives of this study were to quantify the risk for sexual transmission of HCV infection from chronically infected persons to their long-term heterosexual partners and identify specific sexual practices associated with that risk."

The analysis included 500 HCV antibody positive but HIV negative individuals and their long-term heterosexual partners -- the largest such study ever conducted in the U.S. They were recruited in Northern California between 2000 and 2003. The majority of HCV positive people were non-Hispanic whites with a median age of 49 years (range 26 to 79 years). Couples had been in a sexual relationship for at least 3 years, with a median a median of 15 years (range 2 to 52 years). Couples in which both partners were injection drug users were excluded.

Couples were interviewed separately about lifetime risk factors for HCV infection, including injection drug use, sharing personal grooming items such as razors, and sexual activity. Blood samples were tested for HCV antibodies, HCV RNA, and HCV genotype and serotype. Virus was genetically sequenced to determine by phylogenetic analysis whether partners had the same or different virus strains, the latter suggesting sex or other exposures with someone other than the primary partner.

Results

  • In 20 couples (4%), both partners were HCV positive.
  • 9 of these couples had matching HCV genotypes or serotypes.
  • 3 couples (0.6%) had highly related viral isolates, consistent with HCV transmission within the couple.
  • Based upon 8377 person-years of follow-up, the maximum prevalence of HCV infection among sexual partners of people with chronic HCV infection was 1.2%.
  • The maximum incidence rate of HCV sexual transmission was 0.07% per year, or about 1 new infection per 190,000 sexual contacts.
  • No specific sexual practices were found to be associated with both partners in a couple being HCV positive.

"The results of this study provide quantifiable risk information for counseling long-term monogamous heterosexual couples in which 1 partner has chronic HCV infection," the study authors concluded. "In addition to the extremely low estimated risk for HCV infection in sexual partners, the lack of association with specific sexual practices provides unambiguous and reassuring counseling messages."

"Sexual transmission of HCV among monogamous heterosexual couples is an extremely infrequent event," they elaborated in their discussion. "Condom use was infrequent among the study participants and decreased over the duration of the sexual relationship, indicating that the very low rate of sexual transmission in our study population was not due to use of barrier methods during sexual activity."

They noted that their estimates include couples who were both HCV antibody positive but at least 1 partner had undetectable HCV RNA that could not be sequenced to confirm virus relatedness.

"Sexual transmission of HCV presumably occurs when infected serum-derived body fluids are exchanged across mucosal surfaces," they explained. "Potential factors that may influence this exchange include the titer of virus, the integrity of the mucosal surfaces, and the presence of other genital infections (viral or bacterial)."

Studies looking at the presence of HCV RNA in semen, vaginal fluid, cervical smears, and saliva have produced conflicting results, but generally find that levels are undetectable or very low.

"A low titer of virus in genital secretions may be one reason that HCV is transmitted less efficiently than hepatitis B virus or HIV," the researchers wrote. "Additionally, transmission of infection by sex may require a specific genital tract environment such as disrupted mucosal integrity or the presence of viral or bacterial coinfections. These factors may explain the recent reports of HCV transmission by sex in HIV-infected men who have sex with men."

These results "support the current national recommendations that couples not change their sexual practices if they are in a monogamous heterosexual relationship," they concluded.

It must be emphasized that these findings are only applicable to monogamous, HIV negative heterosexuals. People with multiple sex partners, HIV positive individuals (men and women), and gay/bisexual men are at higher risk; there have been no adequate studies of lesbians. Studies to date of HCV sexual transmission among gay men have not shown consistent associations with specific activities, so it is difficult to recommend particular safer sex or other harm reduction strategies.

12/14/12

Reference

NA Terrault, JL Dodge, EL Murphy, MJ Alter, et al. Sexual Transmission of HCV among Monogamous Heterosexual Couples: the HCV Partners Study. Hepatology. November 23, 2012 (Epub ahead of print).