The Effectiveness of Bleach in the Prevention of Hepatitis C Transmission - Final Report

2. Hepatitis C

a) Hepatitis C Virus

HCV is an infectious blood-borne virus first identified in 1989. According to the US Centres for Disease Control and Prevention (CDC), it is the most common chronic bloodborne infection in the United States¹⁷. While 15% to 25% of persons with HCV resolve their infection, the remaining 75% to 85% of cases go onto chronic infection^1,4. Most newly infected persons (60% to 70%) have no symptoms and are unaware of their infection, but are infectious and may spread the virus through high-risk behaviours⁴.

Long term consequences of HCV infection include cirrhosis, hepatocellular carcinoma and other extra-hepatic manifestations^4,5,18,19. HCV is responsible for 40% of chronic liver disease, and HCV-associated end-stage liver disease is the most frequent indication for liver transplantation among adults^6,20. HCV-related chronic liver disease causes 8,000 to 10,000 deaths each year in the United States^6,21 and 800 to 1,000 deaths per year in Canada¹⁹.

While the estimated population prevalence rates are low - approximately 0.8% in Canada^1,3,22 and 1.8% in the United States^6,21 - they increase dramatically among high-risk groups such injection drug users^23,24, incarcerated populations^25,26 and street youth^1,27.

In some cases, HCV can be effectively treated. However, current treatments are only indicated for 20% to 30% of the infected population^20,28. Treatment is effective in 40% to 80% of these cases²⁹, with success dependent on genotype, type of treatment, length of treatment and stage of disease^30,31. There is no vaccine for HCV, and re-infection is possible⁴. This means that prevention relies primarily on the successful interruption of viral transmission and on modification of high-risk behaviours.

b) Modes of Transmission

As many people have multiple risk factors, establishing the exact mode of transmission is often difficult. In the absence of clear risk factors such as IDU, determining which factors - many of which will be forgotten or denied - resulted in transmission is extremely challenging.

Injection Drug Use

In IDU populations, the high HCV prevalence, the high rate of chronic infection, the steady influx of new, susceptible injecting users and the high transmissibility of the virus all contribute to its endemicity^12,15.

There are an estimated 125,000 people who use injection drugs in Canada³² and approximately 1.5 million in the United States³³. The estimated average HCV prevalence in these populations is 80%¹⁵, reaching a high of 90% or more in several communities, including in Vancouver, British Columbia^12,23,24. Worldwide, estimates of HCV prevalence in IDU populations range from 50% to 100%^4,23,24. IDU accounts for at least 60% of all annual HCV infections in the United States and Canada^2,6,15,16.

When injecting drugs, individuals use - and often share - many different pieces of equipment, including needles^a, cookers, swabs, cotton/filters, tourniquets and water. Sharing any of this equipment is a major risk factor for infection^2,34. Thorpe et al. reported that sharing cookers is the most significant predictor of HCV infection after controlling for needle sharing, with an adjusted relative hazard^b (RH) of 4.07. Sharing cotton filters and/or rinse water were also significant predictors of infection in some situations (RH=2.4 & 2.7, respectively)³⁴.

Health Canada's Enhanced Surveillance System for HBV and HCV revealed that, in the period 1998-1999, 78% of injection drug users interviewed reported having shared needles in the six months before diagnosis^1,15. The Vancouver Injecting Drug Use Study (VIDUS) found that of participating individuals who had injected drugs in the six months prior to questionnaire completion, 28% reported sharing needles in that time^35. Likewise, a 1995-1997 New Mexico study found that 90% of participating injection drug users reported sharing injection equipment, primarily with friends (52%) or with their main sex partner (31%). Of those who reported sharing equipment, 85% were anti-HCV positive³⁶. Many of these people are unaware of their HCV infection and engage in more at-risk behaviours than those who are aware of their positive status³⁷.

Equipment sharing is of particular concern among young adults who are newly indoctrinated into the drug culture. A Chicago study found that almost three quarters (74%) of young adult injection drug users - half of whom had just started injecting during the two years prior to enrolment in the study - had shared injection equipment within the previous six months³⁴.

Specific drugs increase the risk of HCV infection. Cocaine use, which often involves up to 20 injections per day, increases the likelihood that drug equipment will be shared⁴. Cocaine is also often inhaled and causes nasal erosions and ulcers, creating the potential for HCV to be transmitted through the sharing of cocaine straws^4,6. Dry and cracked lips, a common side effect of injection drug use, make pipe sharing a potential risk^4,6. Certain injection practices also increase risk. For example, 'front loading' or 'back loading' where drugs are mixed in one syringe and distributed to other syringes, passes potentially infected materials to several people at one time⁴.

Injection drug use and equipment sharing has also made HCV a significant problem in incarcerated populations. Anti-HCV positive rates among inmates in Canada range from 28% to 40%^25,26. While many infections occur outside of prison, transmission has also been documented while in custody, with infection likely a result of IDU³⁸.

Other Modes of Transmission

In the past, a significant number of HCV infections were due to infected blood products^2,13, although in the last decade universal blood donor screening has reduced this risk to approximately 1 in 500,000 donations³⁹.

HCV can also be transmitted during pregnancy and childbirth^9,10 and through needle-stick injury^6,7, sexual contact^6-8, tattooing, body piercing, electrolysis^11,12 and sharing of personal hygiene items such as toothbrushes and razors that may be contaminated with blood^1,12. These modes of transmission, however, account for a very small number of acute HCV infections compared with IDU^1,6,13,14.

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Notes

• In North America, injection drug users most commonly use syringes with non-removable needles, intended for a single use only. This report, therefore, uses the terms "syringe" and "needle" interchangeably.
• 'Relative Hazard' (RH) is the risk of an event, e.g., infection, happening (1.0 is the benchmark or average). In this case, a relative hazard of 4.07 represents a four-fold increase in risk of infection.

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