Profile of Hepatitis C & Injection Drug Use in Canada

HCV in IDU Populations

Consistently, studies of intravenous drug using populations reveal high rates of HCV. This section profiles some of the research conducted in Canada, as well as internationally, by highlighting the perspective that the prevalence of HCV appears to be contingent on the harms associated with IDU, and unlike the HIV population, less related to sexual practices. A summary of the research in this area is provided in Table 2 (see Appendix).

Canada

Strathdee and colleagues (1997) examined the prevalence of HCV, HIV and risk behaviors in a prospective study of individuals who inject drugs from Vancouver, British Columbia. Beginning in May 1996, the Vancouver IDU study recruited persons who had injected drugs at least once in the previous month. Prevalence rates of HCV and HIV were 88% and 23%, respectively. The results also revealed high levels of needle-sharing, with 40% of participants having lent used needles, and 40% having borrowed used needles. As the authors note, the normative nature of needle-sharing is particularly disturbing given that Vancouver has the highest number of needle exchange programs in North America.

Building on the previous study, Patrick et al. (1998) examined incidence and independent predictors of HCV seropositivity in the sample from Vancouver, British Colombia. Among a sample of 1,080 individuals, only 172 were HCV negative at baseline. After a median follow-up of 9.8 months, 23 of these became HCV positive. Factors associated with a positive HCV status included duration of IDU, female gender, history of incarceration, and ever attending a needle exchange program. The authors emphasized the need for primary prevention of IDU, harm reduction in prison and programming for women.

Romanowski et al. (1997) examined risk factors for HCV infection in a sample of 6,668 males and females attending two STD clinics in Alberta. In this group, HCV prevalence was 3.4% and HIV prevalence was 1.5%. The majority (75%) of those who were infected with HCV indicated that they were users of injection drugs. Analyses revealed a significant relationship between hepatitis C infection and IDU, prostitution, exchanging money or drugs for sex and Aboriginal ethnicity.

Stratton and colleagues (1997) employed an interesting approach in their examination of IDU and HCV in a semi-rural region of Nova Scotia. These authors examined seroprevalence of HCV, HBV and HIV among those who inject drugs and their sexual partners (SIDU). IDU among the sexual partner group was not recorded. A total of 172 adults (92 IDU, 80 SIDU) were recruited from the community and local correctional facility. In the IDU group, seroprevalence of HCV was 47%, HBV was 23% and 5% for HIV. Among sexual partners, HCV, HBV and HIV was 1%, 5% and 1%, respectively. Of IDU participants, 71% of males (n=77) and 79% of females (n=15) reported borrowing needles. Based on these findings, the authors concluded that the sharing of needles and HCV infection among persons who inject drugs is not a problem that is restricted to large urban centres.

International

Australia has been prolific in conducting research on the role of IDU in the spread of HCV. In 1997, Crofts and colleagues conducted a review of the available epidemiological data in Australia. The results revealed high rates of HCV, in the magnitude of 60-70%, in populations of Australians who inject drugs. Over a number of studies, with different populations and recruiting methods, a consistent pattern of high HCV infection rates was observed. Infection started with the first injection and continued through the career of the drug injector.

Much of the research examining HCV transmission has been conducted with persons who inject drugs or blood transfusion recipients. Sladden et al. (1997) examined the routes of HCV transmission by conducting a survey of all HCV cases notified to the local public health unit in an Australian community. Of the 467 responses, all but one reported blood exposure: IDU (85%), pre-1990 blood transfusion (6%), other blood exposures (8%). The large majority of respondents were persons who were involved in IDU.

A notable study in the United States is the ALIVE study, a longitudinal investigation of the natural history of HIV in the Baltimore, Maryland area (Garfein et al., 1996; Thomas et al., 1995; Villano et al., 1997). Between 1988 and 1989, 2,921 persons who injected drugs were enrolled in the study. The median duration of drug use was 12 years, and 85% of participants were HCV positive at baseline. Garfein et al. (1996) examined seroprevalence rates among the 716 participants who reported initiation into drug use within the six years before enrollment into the study. Of the 716 participants, 76.9% were HCV positive. Among those who had injected for one year or less, 64.7% were HCV positive. The authors emphasized how the high rate of HCV among short-term injectors highlights the need for early interventions with individuals starting to inject drugs.

Garfein et al. (1998) examined the prevalence and risk factors for HCV in a prospective study of young injection drug users in Baltimore. Recruitment efforts targeted individuals between the ages of 18 and 25 years. Of the 229 participants enrolled, 86 (37.6%) were HCV seropositive at baseline. A positive HCV status was significantly associated with injecting for less than two years. The high HCV prevalence and the strong association with short-term IDU suggest that young adults are at high risk for HCV infection soon after their initiation into IDU. As such, the need for interventions targeted early in IDU or at those at risk for starting IDU is essential.

Chang and colleagues (1999) specifically examined the relationship between the prevalence of HCV infection and duration of drug use in a sample of 899 drug users from Taiwan. The prevalence of HCV was 67.2% among those who injected drugs, and 14.7% among those that did not inject drugs. HCV infection was positively associated with duration of injection use within the first seven years of drug use. The steepest trajectory in HCV infection occurred within the first four months of IDU. Consistent with the findings of other studies discussed, these results highlight the importance of early risk reduction and prevention interventions in reducing HCV infection rates.

The research findings from Canada regarding the role of IDU in the transmission of HCV are consistent with those obtained internationally. Populations with a higher occurrence of IDU activity have a correspondingly higher rate of HCV; for example, 88% in Vancouver, Canada (Strathdee et al., 1997), 85% in Baltimore, United States, 85% in Australia (Sladden, 1997). Studies that examined HCV infection among individuals with health issues other than IDU had a much lower rate of HCV prevalence: 3.4% in a sexually transmitted disease clinic in Alberta, Canada (i.e. Romanowski et al., 1997), 14.7% among a sample of people who use drugs (noninjection drug use) in Taiwan (Chang et al., 1999).

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