Hepatitis C: An Overview

Transmission

How is hepatitis C being transmitted?

Routes of Transmission Pie Chart
Injecting Drug Use
- Accounts for 60 percent of HCV transmission
- Accounts for two-thirds of new infections
- Highly efficient mode of transmission
- Prevalence in injecting drugs using populations is high
- Rapidly acquired after first injection

Prevalence of HCV and HIV in IDUs
Location	Year	HCV	HIV
Amsterdam	1991	66%	33%
Geneva	1992	80%	32%
Baltimore	1994	90%	25%
Seattle	1999	82%	2%
Rural UK	2000	56%	14%
S. China	2003	71%	17%
Vancouver	2004	44%	19%

Studies of Young or New Injectors
- Baltimore (Thomas, et. al): Reported 80 percent prevalence in subjects acknowledging two years of injection drug use or less.
- Chicago and Suburbs (Thorpe, et. al):
  - Reported 27 percent prevalence in subjects age 18 to 30
  - Reported 15 percent prevalence in subjects acknowledging two years of injection drug use or less.
Studies of Young or New Injectors
- Seattle (Hagan et. al):
  - Reported 41 percent antibody prevalence in subjects acknowledging drug use for two years or less at time of enrollment.
  - Mean time to seroconversion:
    - 0.6 years for those positive at enrollment
    - 5.4 years for those negative at enrollment who later seroconverted
    - 3.4 years weighted average time to seroconversion
Factors Associated with Infection
- Years of injecting
- Frequency of injection
- Being a young/new injecting drug user
- Sharing syringes
- Sharing cotton/cookers
- Backloading
Sexual Transmission
- 15 percent of HCV infection
- However, sex is an inefficient mode of transmission
- Long-Term Spouses (CDC)
  - A low prevalence of HCV infection has been reported by studies of long-term spouses of patients with chronic HCV infection who had no other risk factors for infection.
  - Five of these studies have been conducted in the United States, involving 30-85 partners each, in which average prevalence was 1.5% (range: 0% to 4.4%)
Long-Term Prospective Study (Vandelli et. al.)
- Enrolled anti-HCV negative partners of HCV positive individuals.
- 776 partners completed a ten-year follow-up.
- Three spouses acquired HCV during follow-up.
- All had other risk factors and/or follow-up testing showed genotype/strain discordant with that of spouse.
Sexual Transmission
- Risk higher among those with multiple partners and history of sexually transmitted disease
- Prevalence found to average 5 percent among STD clinic patients with no history of injection drug use.
- Factors associated with positivity
  - Greater number of sex partners
  - History of STDs
  - Failure to use a condom
Transfusion
- 1990
  - Routine testing of donors was initiated.
  - Risk was approximately 1.5% per recipient or approximately 0.2% per unit transfused.
- July 1992
  - More sensitive testing was implemented.
  - Reducing risk for infection to 0.001% per unit transfused.
- 2005
  - Current risk for transfusion-associated hepatitis C is 1 per 2 million units transfused.
Blood Clotting Factor
- Used to treat individuals with hemophilia.
- High risk of infection prior to the use of virus inactivation procedures that were introduced in 1985 and 1987.
- Prevalence is greater than 90 percent in hemophiliacs treated with these products before inactivation.
Solid Organ Transplants
Occupational

Occupational exposure is inefficient.
In one study that evaluated risk factors for infection, a history of unintentional needle-stick injury was the only occupational risk factor independently associated with HCV infection.
Average incidence 1.8 percent following needle stick from HCV-positive source.
Prevalence among health care workers is 1 to 2 percent.

Nosocomial Transmission
- Rarely reported in the United States, other than in chronic hemodialysis settings.
- Prevalence of anti-HCV positivity among chronic hemodialysis patients averages 10%.
- Studies have documented an association between anti-HCV positivity and increasing years on dialysis.
- Most likely due to incorrect implementation of infection-control practices.
Perinatal
- Five percent of infected mothers transmit the virus to their baby.
- Average rate of transmission is higher in women also infected with HIV – 17 percent.
- No difference seen between vaginal and cesarean births.
Household Transmission
- Rare but not absent
- Could occur through percutaneous/mucosal exposure to blood
  - Contaminated equipment for home therapies
  - Theoretically through the sharing of personal items (I.e., toothbrushes, razors)
No Known Risk
- In 10 percent of cases, no known risk is identified.
Exposures in Other Settings (CDC)
- No data or insufficient data to show transmission through:
  - Intranasal cocaine use
  - Tattooing
  - Piercing