Sexual Activity as a Risk Factor for
Hepatitis C Infection

Norah A. Terrault, MD, MPH

NIH Consensus Development Conference on
Management of Hepatitis C: 2002 

Bethesda, Maryland
June 10-12, 2002

Percutaneous exposures are well-recognized risk factors for Hepatitis C Virus, hepatitis B virus (HBV), and HIV. However, there are clear differences between these viruses with respect to their frequency of transmission through sexual contact. The accumulated epidemiological evidence indicates that Hepatitis C Virus can be sexually transmitted but much less efficiently than HBV and HIV. Epidemiological studies evaluating the magnitude of risk of Hepatitis C Virus transmission by sexual activity have several methodological shortcomings that tend to overestimate the proportion of Hepatitis C Virus infections associated with sexual contact.

Early studies used first-generation anti-Hepatitis C Virus assays, which have a higher false positive rate than second- and third-generation assays. Studies vary in the completeness of risk ascertainment and many fail to carefully exclude Hepatitis C Virus acquisition from non-sexual sources. Non-disclosure of injection drug use (IDU) as a risk factor is particularly important since assessing the contribution of sexual activity to Hepatitis C Virus transmission is difficult in the presence of IDU. Finally, only a limited number of studies perform virological analyses to confirm that sexual partners are infected with the same virus and to exclude acquisition from outside sources.

Reported rates of Hepatitis C Virus infection in sexual partners differ by geographical region, with higher rates reported in countries with higher endemic rates of Hepatitis C Virus infection. Rates of anti-Hepatitis C Virus positivity also vary by risk group, with higher rates of Hepatitis C Virus reported in persons with a history of sexually transmitted diseases (STDs) and lower rates in heterosexual partners in long-term relationships. This difference may reflect the frequency of exposure to different Hepatitis C Virus-infected sexual partners (higher in those with multiple partners than those in monogamous relationships). Alternatively, these risk groups may reflect differing rates of exposure to other non-sexual sources of Hepatitis C Virus, such as IDU. The findings regarding sexual transmission in one group may not be generalizable to other groups or to the general population.

How Prevalent is the Risk Factor “Sexual Activity” in Persons With Acute Hepatitis C?

The Centers for Disease Control and Prevention collects detailed risk factor data on newly diagnosed cases of acute hepatitis C. In these surveillance studies, 15–20 percent of cases of acute community-acquired Hepatitis C Virus occur in persons who report unprotected sexual contact with an anti-Hepatitis C Virus positive person in the preceding 6-month period (two-thirds of cases) or multiple sexual partners (one-third of cases) as their only risk factor for Hepatitis C Virus acquisition. Limited access to the sexual contacts prevents virological evaluation of the transmission events.

What is the Prevalence of Hepatitis C Virus in Persons at Risk for Sexually Transmitted Diseases?

In U.S. seroprevalence studies conducted among sex workers, persons attending STD clinics, or persons participating in HIV surveillance studies, 1.6–25.5 percent of individuals are anti-Hepatitis C Virus positive. In studies including persons with a history of IDU, anti-Hepatitis C Virus positivity is more strongly associated with IDU than with factors related to sexual practices. In studies limited to individuals without a history of IDU, anti-Hepatitis C Virus positivity is identified in 1.6–7 percent of STD clinic attendees, and risk factors associated with Hepatitis C Virus are number of recent and lifetime partners, high-risk sexual contact (variably defined), and anti-HIV positivity. In homosexual and bisexual men, rates of anti-Hepatitis C Virus positivity range from 2.9–12.7 percent with higher rates amongthose with HIV infection, but again IDU rather than sexual risk factors is most strongly associated with being Hepatitis C Virus-positive.

What is the Prevalence of Hepatitis C Virus in Monogamous Heterosexual Couples?

Among steady heterosexual partners of Hepatitis C Virus-infected, HIV-negative persons, 0–24 percent are anti-Hepatitis C Virus positive, with marked geographical variability. The median rate of anti-Hepatitis C Virus positivity in sexual partners is 1.0 percent in North America and Northern Europe, 6 percent in Southern Europe, and 11 percent in Southeast Asia. Studies using genotyping or viral sequence analysis to assess anti-Hepatitis C Virus concordant couples find lower rates of Hepatitis C Virus transmission than studies using antibody testing alone. The duration of the sexual relationship is not predictive of Hepatitis C Virus positivity in partners after adjusting for age. In studies comparing Hepatitis C Virus positivity among sex partners vs. other family members, the rates of Hepatitis C Virus positivity are higher in spouses than in other family members. However, after controlling for age and other parenteral exposures, anti-Hepatitis C Virus positivity is no longer consistently associated with the type of relationship.

The majority of the published studies use genotyping rather than viral sequence analysis to evaluate anti-Hepatitis C Virus concordant couples. Genotyping is suboptimal since Hepatitis C Virus genotypes that are prevalent in the population may be present in partners even though they may have acquired  he virus from different sources. For example, a study of 24 anti-Hepatitis C Virus concordant couples found that 12 had concordant genotypes, 7 had discordant genotypes, and 5 were untypable. Seven of the 12 couples could be analyzed by sequence analysis, and only 3 were highly homologous and consistent with transmission. Thus, overestimation of Hepatitis C Virus sexual transmission occurs if genotyping rather than sequence analyses is used to evaluate infected partners.

What is the Incidence of Hepatitis C Virus Infection in “At Risk” Individuals?

In prospective studies (1–3.7 years followup) conducted in high-risk cohorts of non-IDU sex workers and patients in STD clinics, the incidence of Hepatitis C Virus is 0.4–1.8/100 person-years (~1 percent). Small sample size precludes evaluation of specific sexual practices as risks for Hepatitis C Virus acquisition. Undisclosed IDU may contribute the higher incidence of infection in this subgroup.

Based upon results from a prospective cohort of 499 Italian couples followed for a mean of 12.4 months, the incidence of new infection in sexual partners is 12 per 1,000 person-years. Sequence analysis of the Hepatitis C Virus-positive couples reveals a high degree of sequence homology in only 50 percent of the couples, suggesting non-sexual sources of Hepatitis C Virus acquisition and a true incidence of no more than 6 per 1,000 person-years. In retrospective cohorts of female partners  of hemophiliacs, the incidence is 1 to 1.87 per 1,000 person-years; among male partners of women infected by contaminated anti-D immunoglobulin, the incidence is 0.28 per 1,000 person-years; and among liver clinic patients and their sexual partners, the incidence is 1 to 3.86 per 1,000 person-years.

Factors That May Affect the Risk of Hepatitis C Virus Transmission by Sexual Contact

In studies involving persons at risk for STDs, HIV co-infection is an independent predictor of anti-Hepatitis C Virus positivity in the majority of studies. In studies involving hemophiliacs with HIV and Hepatitis C Virus, the rate of anti-Hepatitis C Virus positivity is higher in female partners of dually-infected men compared to men with Hepatitis C Virus infection only. Studies from STD clinic attendees also suggest that co-infection with other STDs or sexual practices which may traumatize the mucosa (anal receptive sex) may increase the risk of sexual transmission of Hepatitis C Virus.

Whether the risk of Hepatitis C Virus transmission differs for males vs. females is unclear. In one study of heterosexual couples in STD clinics, females with Hepatitis C Virus-positive partners were 3.7 times more likely to have Hepatitis C Virus than females with Hepatitis C Virus-negative partners; this pattern was not evident in males. The titer of Hepatitis C Virus RNA and Hepatitis C Virus genotype do not appear to influence the risk of Hepatitis C Virus transmission, but high-quality studies to assess these virological factors are lacking.

Summary

The available data indicate that Hepatitis C Virus can be sexually transmitted but the efficiency of transmission by the sexual route is low. The risk of sexual transmission of Hepatitis C Virus is estimated to be 0.03 percent to 0.6 percent per year for those in monogamous relationships, and 1 percent per year for those with multiple sexual partners.

Given these estimates of risk, the current recommendations are:

1. Hepatitis C Virus-positive individuals in longer-term monogamous relationships need not change their sexual practices. If couples wish to reduce the already low risk of Hepatitis C Virus transmission by sexual contact, barrier precautions may be used. Partners of Hepatitis C Virus-positive persons should be considered for anti-Hepatitis C Virus testing.

2. For Hepatitis C Virus-infected individuals with multiple or short-term sexual partners, barrier methods or abstinence are recommended. Additional common-sense recommendations include the use of barrier precautions if other STDs are present, if having sex during menses, or if engaging in sexual practices that might traumatize the genital mucosa. Finally, couples should not share personal items that may be contaminated by blood such as razors, toothbrushes, and nail-grooming equipment.

References

LINK TO FULL-TEXT ARTICLE
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