What is the risk of contracting hepatitis C (HCV) through unprotected anal sex with a partner who has hepatitis C (HCV)?

Risk of Hepatitis C Transmission Through Unprotected Anal Sex

The risk of contracting hepatitis C through unprotected anal sex with an HCV-positive partner is low but significantly elevated compared to other forms of sexual contact, particularly when combined with HIV coinfection, multiple partners, or traumatic sexual practices. 1

Risk Stratification by Sexual Context

Monogamous Heterosexual Relationships

• For stable, long-term monogamous heterosexual couples, the transmission risk is extremely low to essentially zero. 2, 3
• A 10-year prospective study following 895 monogamous heterosexual couples documented zero confirmed sexual transmissions over 8,060 person-years of follow-up, yielding an incidence rate of 0 per 1,000 person-years (95% CI: 0-6.3 per 10,000 unprotected contacts). 3, 4
• Condom use is not recommended for monogamous heterosexual couples given this negligible risk. 1, 2

High-Risk Sexual Scenarios

The risk increases substantially with specific high-risk factors: 1, 5

• Multiple sexual partners: Risk increases to 0.4-1.8% per year with multiple partners 2
• Unprotected anal intercourse: Specifically identified as a higher-risk activity compared to vaginal intercourse 1
• Traumatic sexual practices: Fisting and "hard" sexual practices causing mucosal bleeding significantly increase transmission risk 6, 7
• Concurrent sexually transmitted infections: Particularly rectal infections like lymphogranuloma venereum (LGV) or syphilis that cause mucosal lesions 8, 6, 7
• HIV coinfection: HIV-positive individuals face substantially higher sexual transmission risk 2, 8

Men Who Have Sex With Men (MSM)

Among HIV-positive MSM engaging in high-risk sexual practices, HCV transmission through anal sex is well-documented and represents an emerging public health concern. 8, 6, 7

Evidence from MSM Populations

• A cluster investigation found 41% (7 of 17) HIV-positive MSM recently seroconverted for HCV, with unprotected fisting practiced by all seven infected men compared to only two of nine uninfected men (P = 0.003). 7
• Multiple case series from Paris identified 29 cases of acute HCV in HIV-positive MSM between 2001-2004, with 76% reporting unprotected anal sex, 21% reporting fisting, and 41% having concomitant STIs. 6
• Six of seven HCV seroconversions occurred in men with concurrent LGV proctitis, suggesting mucosal inflammation facilitates transmission. 7

Specific Risk Factors in MSM

• Unprotected receptive anal intercourse with multiple partners 9
• Bleeding during sex and traumatic practices (fisting reported in 100% of infected vs 22% of uninfected in one study) 6, 7
• Concomitant STIs causing rectal inflammation (LGV, syphilis) 8, 6
• HIV coinfection (86% of HCV-infected MSM were HIV-positive in cluster studies) 7

Mechanism of Transmission

HCV sexual transmission occurs through mucosal exposure to blood, with efficiency related to viral load and mucosal integrity. 2, 5

• Higher HCV RNA viral loads increase transmission probability. 2, 9
• Sexual transmission is much less efficient than hepatitis B virus or HIV transmission. 2, 9
• Anal intercourse poses higher risk than vaginal intercourse due to increased likelihood of mucosal trauma and bleeding. 1
• Sex accompanying wounds or bleeding significantly elevates risk. 1

Prevention Recommendations

For Monogamous Couples

• No barrier protection required given the extremely low transmission risk in stable heterosexual relationships. 1, 2, 5
• Partner testing provides reassurance but is not mandatory. 2

For Multiple Partners or High-Risk Practices

• Use latex condoms consistently and correctly for all anal and vaginal intercourse. 2, 5
• Reduce number of sexual partners. 5
• Avoid traumatic sexual practices that cause bleeding. 6, 7
• Screen for and treat concurrent STIs promptly. 5

For HIV-Positive MSM

• Annual HCV screening is recommended for HIV-positive men engaging in unprotected sex with men. 9
• Strongly advocate safer sex practices and condom use. 6
• Consider more frequent screening (case-by-case basis) for those with ongoing high-risk behaviors. 9

Critical Caveats

The discrepancy between negligible risk in monogamous heterosexual couples versus documented transmission in HIV-positive MSM populations highlights that context is everything. 3, 8, 6, 7

• Unacknowledged injection drug use may confound some sexual transmission reports, though recent cluster investigations with detailed contact tracing have confirmed sexual transmission. 1, 7
• The presence of HIV coinfection appears to be a critical cofactor, possibly through increased HCV viral loads or altered mucosal immunity. 8, 6, 7
• Single exposure risk remains difficult to quantify precisely, but is clearly higher with anal intercourse, bleeding, and HIV coinfection compared to protected vaginal intercourse in HIV-negative individuals. 1, 2