How is Hepatitis C (HCV) spread?

How Hepatitis C Virus Spreads

Hepatitis C virus (HCV) is transmitted primarily through blood-to-blood contact via percutaneous or permucosal exposure to infected blood, with injection drug use currently representing the dominant mode of transmission in developed countries. 1

Primary Routes of Transmission

Blood Exposure (Most Efficient)

• Injection drug use is the most important current route of HCV transmission in developed countries, with 50-90% of intravenous drug users becoming infected and accounting for 68% of newly acquired cases in the United States 1
• HCV is acquired more rapidly after initiating injection drug use compared to other bloodborne viruses, with up to 90% of users infected within 5 years of starting 1
• Blood transfusions and organ transplantation were major transmission routes until 1991, but screening has virtually eliminated this risk in developed countries 1
• Needlestick injuries carry a transmission risk of 1.8% (range 0-7%) in most countries and 0.92% in South Korea 1
• Healthcare workers have no higher prevalence than the general population (1-2%) despite occupational exposure 1

Unsafe Medical Procedures

• Unsafe injection practices with multiple-use medication vials, reused syringes, or unsanitary medical procedures (surgery, endoscopy, dental treatment) are the main causes of HCV transmission in developing countries 1
• Hemodialysis patients show average anti-HCV prevalence of 10%, with some centers reporting rates exceeding 60%, primarily due to inadequate infection control practices 1
• Tattooing, piercing, and acupuncture without proper disinfection are documented risk factors 1

Sexual Transmission (Inefficient but Documented)

Risk Stratification

• Long-term monogamous heterosexual relationships show very low transmission risk, with average HCV prevalence of only 1.5% among steady spouses 2
• Multiple sexual partners is the most consistently identified sexual risk factor, with thresholds including: more than 2 partners in 6 months for acute hepatitis C, ≥5 partners/year for blood donors, and ≥10 lifetime partners in the general population 1, 2
• High-risk sexual practices including anal sex, sex with wounds, concurrent sexually transmitted diseases (especially HIV), and male-to-male sexual contact increase transmission risk 1
• Male-to-female transmission appears more efficient than female-to-male transmission 2

Important Caveat

Sexual transmission of HCV is inefficient compared to other bloodborne viruses, and the overall data show considerable inconsistencies 1. The prevalence among men who have sex with men is generally similar to heterosexuals in STD clinic settings, raising questions about whether unacknowledged injection drug use contributes to apparent sexual transmission 1.

Perinatal Transmission

• Vertical transmission rate is 5-6% for HCV-positive, HIV-negative mothers and increases to 14-17% for HCV/HIV coinfected mothers 1
• The rate is 1.7% when mothers are anti-HCV positive regardless of RNA status, and 4.3% (range 3.9-7.1%) when mothers are HCV RNA-positive 1
• The only consistent predictor of transmission is presence of HCV RNA in the mother at delivery 1
• Risk factors for increased transmission include: HIV coinfection, high maternal HCV RNA levels, and female infant gender 1
• Cesarean delivery does not prevent transmission and is not recommended solely for HCV indication 1
• Breastfeeding transmission has not been documented and is not contraindicated unless nipples are cracked or bleeding 1

Household and Other Exposures

• Nonsexual household contact shows average anti-HCV prevalence of 4% among contacts, likely through direct or inapparent percutaneous/permucosal exposure to blood 1
• Sharing of personal items that may contact blood (razors, toothbrushes, nail clippers) represents a potential transmission route 1
• Intranasal cocaine use has been associated with HCV infection in some studies, possibly through sharing contaminated straws, though this appears uncommon as a sole risk factor 1

Clinical Implications for Prevention

• Universal screening in pregnancy is now recommended by the CDC and USPSTF 1
• Screen HCV-positive patients for other sexually transmitted infections including HIV, syphilis, gonorrhea, chlamydia, and hepatitis B 1
• Vaccinate against hepatitis A and B viruses if not immune 1
• Counsel patients to avoid donating blood, organs, tissues, or semen, and not to share any instruments that penetrate skin 1
• For monogamous couples, barrier protection is not necessarily recommended given the very low transmission risk 1
• For those with multiple partners or high-risk sexual practices, latex condoms should be used correctly and consistently 2