What are the primary modes of hepatitis C transmission?

Primary Modes of Hepatitis C Transmission

Hepatitis C virus (HCV) is primarily transmitted through parenteral exposure to infected blood, with injection drug use currently accounting for most new infections in developed countries, while unsafe medical procedures remain the main cause in developing regions.

Main Routes of HCV Transmission

Parenteral Blood Exposure

• Injection Drug Use: Currently the most common route of transmission in developed countries, accounting for 60-70% of new infections 1

  • HCV infection is acquired rapidly after initiation of injecting drug use
  • Up to 90% of users become infected within 5 years 1
  • HCV spreads through sharing syringes, needles, and drug preparation equipment

• Blood Transfusion and Blood Products: Historically significant but now rare in countries with screening

  • Was a major route until 1991 when screening was implemented 1
  • Current risk is extremely low (approximately 0.001% per unit transfused) 1
  • Hemophiliacs treated with clotting factors before viral inactivation procedures (pre-1985) have HCV infection rates up to 90% 1

• Organ Transplantation: High risk from infected donors before screening implementation 1

• Healthcare-Related Exposures:

  • Needlestick injuries: Risk of 1.8% (0-7%) globally, 0.92% in South Korea 1
  • Unsafe medical procedures: Major cause in developing countries 1
  • Includes reuse of syringes, multiple-use medication vials, inadequate sterilization during surgery, endoscopy, and dental procedures 1

• Other Percutaneous Exposures:

  • Tattooing, piercing, and acupuncture without proper sterilization 1
  • Sharing personal items that may have blood contact (razors, toothbrushes) 1

Sexual Transmission

• Generally inefficient but possible, especially in certain circumstances:
  • Low risk in monogamous relationships (<5%) 1
  • Higher risk with:
    • Multiple sexual partners 1
    • Unsafe sex practices including anal sex 1
    • Sex accompanying wounds 1
    • Coinfection with other sexually transmitted diseases, especially HIV 1
    • Homosexual men with HIV infection 1

Perinatal (Mother-to-Child) Transmission

• Overall risk: 1-6.2% 1
  • 1.7% when mothers are anti-HCV positive regardless of RNA status 1
  • 4.3% when mothers are HCV RNA-positive 1
  • Risk factors for increased transmission:
    • Female infants 1
    • HIV-positive mothers 1
    • High maternal HCV viral load 1
  • Cesarean section does not prevent transmission 1
  • Breastfeeding poses minimal risk unless nipples are injured or bleeding 1

Prevention Strategies

Individual Prevention Measures

• HCV-infected persons should:
  • Not donate blood, organs, tissues, or semen 1
  • Not share items that could have blood contact (toothbrushes, razors, nail clippers) 1
  • Use barrier protection if having multiple sexual partners 1

Healthcare Setting Prevention

• Proper sterilization and disinfection of medical equipment 1
• Safe injection practices 1
• Standard precautions for healthcare workers 1

Specific Populations

• Pregnant Women:

  • Universal screening recommended 1
  • No restriction on breastfeeding unless nipples are cracked or bleeding 1
  • Avoid internal fetal monitoring and early artificial rupture of membranes when possible 1

• Injection Drug Users:

  • Primary prevention of drug use 2
  • Harm reduction strategies including needle exchange programs 2

Important Caveats

• No effective vaccine exists for HCV prevention 1
• Approximately 10% of infections have no identifiable source 3
• HCV is not transmitted through casual contact, sharing meals, sneezing, or coughing 1
• The high rate of chronic infection (55-85% of cases) creates a large reservoir of infectious individuals 1

Understanding these transmission routes is crucial for implementing effective prevention strategies and reducing the global burden of HCV infection and its complications, including chronic liver disease, cirrhosis, and hepatocellular carcinoma.