Epi-Update
Hepatitis C Virus Infection among Injecting Drug Users (IDU) in Canada: Results from I-track (2003-2005)

Introduction

Hepatitis C is caused by infection with the hepatitis C virus (HCV), which was first identified in 1989.  HCV is transmitted through contact with infected blood and blood products.  HCV is one of the major causes of liver failure and transplant in the developed world¹.

Initial (acute) infection with HCV is largely asymptomatic, with mild illness occurring in less than 25% of those infected².  Some infected individuals recover from their infection, but 75-85% progress to the chronic (carrier) state³.  In these individuals, up to 20% will develop cirrhosis of the liver, often after two or more decades without symptoms.  Due to its “silent” nature, approximately one-third of chronically infected individuals are unaware of their infection, increasing the risk that they could transmit the virus to others⁴.  Currently, there is no vaccine for HCV.

Currently, injection drug use (IDU) is the dominant risk factor for HCV transmission in Canada (due to sharing of needles, syringes, and other injection equipment), and is implicated in 70-80% of recent HCV cases in Canada.  Sharing of equipment for inhalation drug use (e.g. crack pipes, straws, etc.) has also been associated with HCV transmission.  In larger Canadian cities, travel or residence in a HCV-endemic region is also a common risk factor, because of the higher rate of health care-acquired HCV infections in these areas.  Sexual and perinatal (mother-to-child) transmission is inefficient and occurs uncommonly.  Elevated risk is associated with tattooing or body piercing with contaminated equipment, or the sharing of personal hygiene items (e.g. razors, toothbrushes) with someone infected with HCV.  While there have been cases of HCV transmission via contaminated blood transfusions, the enhanced screening procedures of Canada’s blood supply since 1990 has virtually eliminated this risk⁴.

The purpose of this document is to examine the prevalence and risk factors for HCV infections among injecting drug users (IDU) in Canada. Information presented is based on data collected during Phase 1 of I-Track, a multicentre, enhanced surveillance system that describes changing patterns in drug injecting practices, sexual risk behaviours, HIV and HCV prevalence and testing behaviours among IDU in Canada⁵. Phase 1 of I-Track was completed between October 2003 and May 2005. In this phase, there were 3031 participants recruited from seven sites (Victoria, Edmonton, Regina, Winnipeg, Sudbury, Toronto, and the SurvUDI sites (Abitibi-Témiscamingue, Estrie, Mauricie / Centre du Québec, Montérégie, Montréal, Ottawa, Outaouais, Québec, Saguenay / Lac St-Jean]). For more information about Phase 1 of I-Track, please refer to the Enhanced Surveillance of Risk Behaviours among Injecting Drug Users in Canada report which can be retrieved at http://www.phac-aspc.gc.ca/i-track/sr-re-1/index-eng.php.

Unless otherwise stated, the analyses presented here are restricted to those IDU participating in I-Track who consented to provide blood for HCV testing and who had definitive HCV results (n = 2,842).

Results

HCV prevalence: Almost two-thirds of IDU were HCV positive.

• Between 2003 and 2005, the prevalence of HCV was 65.7% (average across seven sites).
• Site-specific HCV prevalence rates ranged from 61.8% to 68.5%.

HCV demographics: Older IDU were more likely to be infected with HCV.

Compared to those under the age of 20, IDU aged 40+ years were nearly thirty times as likely to be HCV positive (Table 1).

Table 1: Demographics

	Total (n)	HCV+ (%)	OR (95% CI)	p-value
Gender
Male	1982	1292 (65.2)	Ref
Female	843	549 (65.1)	1 (0.8-1.2)	0.97
Age group
<20 years	101	12 (11.9)	Ref
20-29 years*	747	362 (48.5)	6.9 (3.8-13.0)	<0.0001
30-39 years*	942	641 (68.1)	15.8 (8.5-29.3)	<0.0001
40-49 years*	824	658 (79.9)	29.4 (15.7-55.0	<0.0001
50+ years*	206	165 (80.1)	29.8 (14.9-59.7)	<0.0001
Level of education
Completed less than high school level	2111	1363 (64.6)	0.92 (0.8-1.1)	0.37
Completed high school or more	703	467 (66.4)	Ref
Ethnicity
Aboriginal	746	490 (65.7)	1.03 (0.9-1.2)	0.73
Non-aboriginal	2059	1338 (65.0)	Ref

* Statistically significant at p<0.05; OR (95% CI) = odds ratio (95% confidence interval)

Drug use and injecting practices: IDU who had injected cocaine or crack and cocaine in the last six months, who had injected in a public place in the last six months and who had injected more than one or two times per week in the last month were more likely to be infected with HCV (Table 2).

• IDU who had injected cocaine or crack and cocaine in the last six months were almost twice as likely to be infected with HCV compared to those who didn’t.
• Those injecting regularly (more than 1-2 times per week) in the last month were 1.4 times more likely to be infected with HCV compared to those who reported injecting “sometimes or never” in the last month.
• Those injecting in a public place in the last six months were 1.5 times more likely to be infected with HCV than those who didn’t report injecting in a public place.

Table 2: Drug use and injecting practices among IDU

	Total (n)	HCV+ (%)	OR (95% CI)	p-value
Injected cocaine in the last 6 months*
Yes	2346	1590 (67.8)	1.9 (1.5-2.3)	<0.0001
No	492	260 (52.9)	Ref
Injected crack and cocaine in the last 6 months*
Yes	2432	1640 (67.4)	1.9 (1.6-2.4)	<0.0001
No	406	210 (51.7)	Ref
Frequency of injection in the last month*
Regularly. more than one or two times per week	2021	1362 (67.3)	1.4 (1.2-1.7)	<0.0001
Sometimes or never	821	490 (59.7)	Ref
Injected in a public place in the last 6 months*
Yes	2591	1709 (66.0)	1.5 (1.2-2.0)	0.0024
No	222	124 (55.9)	Ref
Most frequent place of injection
Public	684	448 (65.6)	1.02 (0.9-1.2)	0.81
Others	2097	1363 (65.0)	Ref

*Statistically significant at p<0.05; OR (95% CI) = odds ratio (95% confidence interval)

Sharing of needles and injecting equipment: Needle exchange program (NEP) users and those who had borrowed needles in the last six months were more likely to be infected with HCV (Table 3).

• Compared to HCV negative IDU, those who were HCV positive were almost three times more likely to use NEPs.
• HCV positive IDU were also 1.5 times more likely to have borrowed needles in the last six months than HCV negative IDU.

Table 3: Needle exchange and injecting equipment sharing practices among IDU

	Total	HCV+ (%)	OR (95% CI)	p-value
Any Needle Exchange Program use*
Yes	2530	1722 (68.1)	3.13 (2.4-4.0)	<0.0001
No	301	122 (40.5)	Ref
Borrowed needles in the last 6 months*
Yes	578	418 (72.3)	1.51 (1.2-1.8)	<0.0001
No	2223	1409 (63.4)	Ref
Borrowed equipment in the last 6 months
Yes	856	551 (64.4)	0.95 (0.8-1.1)	0.52
No	1947	1278 (65.6)	Ref
Borrowed needles in the last month
Yes	1501	974 (64.9)	1.01 (0.9-1.2)	0.87
No	1180	762 (64.6)	Ref
Borrowed equipment in the last month
Yes	1479	962 (65.0)	1.01 (0.9-1.2)	0.93
No	1170	759 (64.9)	Ref

* Statistically significant at p<0.05; OR (95% CI) = odds ratio (95% confidence interval)

Sexual behaviours: Female IDU who were sex trade workers in the last six months were 1.7 times more likely to be infected with HCV than female IDU who had not been involved in sex trade work in the past 6 months (Table 4).

Table 4: Sexual behaviours in IDU, 2003-2005, Canada

	Total (n)	HCV+ (%)	OR (95% CI)	p-value
Sex trade worker in the last 6 months (female)*
Yes	250	182 (72.8)	1.7 (1.2-2.3)	0.0022
No	589	364 (64.8)	Ref
Sex with male sex partners in the last 6 months (male)
Yes	186	119 (64.0)	0.9 (0.7-1.3)	0.7
No	1776	1161 (65.4)	Ref

* Statistically significant at p<0.05; OR (95% CI) = odds ratio (95% confidence interval)

HCV/HIV Co-infection

• Of those IDU with known HCV and HIV laboratory test results, the HCV-HIV co-infection rate was 14%
• With site-specific weights, the HCV-HIV co-infection rate was 11.7%
• Among those who were HCV positive, 21% were also HIV positive; among those who were HIV positive, 91% were HCV positive.
• Site-specific variation in co-infection rates ranged from 0.2% to 8.7% 

Testing behaviours: The vast majority of IDU reported a previous testing history for HCV (Table 5).

• On average, 85.2% of IDU reported having been previously tested for HCV and the testing rates were similar across all participating sites.
• Among HCV positive IDU with a previous history of HCV testing, 37.4% were tested within the past 6 months but a similar proportion (33.1%) also reported their last test was conducted over two years ago.
• Overall, 52.6% of participants reported having been tested for HCV in the previous 12 months.

• 12.7% of IDU reported being tested for HCV for the first time.
• Among HCV-positive participants, 11.4% were not aware of their infection.

• The proportion of IDU reporting HCV testing within the past six months varied between sites from 19.3% to 44.8%.
• These numbers are based on those who tested positive for HCV and do not reflect the testing patterns of people who considered themselves HCV negative.

 

 

Accessing care: More than a half of IDU who knew their positive HCV infection status reported accessing care.

• Overall, 51.5% of IDU who were aware of their positive HCV status reported one or more visits to a physician in the previous six months.
• Access to care varied by site from 43.1% to 56.1% of HCV positive IDU reporting at least one visit to a physician’s office in the previous six months

• Overall, 7.3% of HCV positive IDU were taking medication to treat their HCV infection but this proportion varied across sites from 2.9% to 12.8%.

Discussion

Results from Phase 1 I-Track indicate that HCV prevalence remains unacceptably high among IDU in this study population at 65.7% when compared to the estimated HCV prevalence of 0.8% in the general Canadian population. Approximately 1 in 7 (14%) of IDU were co-infected with HCV and HIV. Older (and more likely established) IDU were more likely to be HCV-infected relative to their younger counterparts. Like other studies, risk factors such as cocaine and crack use, borrowing needles and frequency of injection were independently associated with HCV prevalence (data not shown). Although NEP attendance was positively associated with a positive HCV status, published reports suggest that NEPs attract higher risk IDU ^6,7,8. This observation provides one explanation for the higher proportion of HCV positive participants among NEP users and also suggests that these venues provide a good opportunity to reach and provide prevention and care services to these higher-risk individuals. One third of HCV positive IDU had been tested for HCV within the past six months and of those testing positive, nearly one half accessed care within the previous six months. Given the rapidly changing drug culture in urban and semi-urban centres across Canada, it is important for prevention, treatment, and care services to be responsive to the local needs. It is also important not to overlook the social and contextual factors that may be associated with HCV transmission.

References

1. World Health Organization.  Viral Cancers: Hepatitis C.  Retrieved April 3, 2008 from http://www.who.int/vaccine_research/diseases/viral_cancers/en/index2.html
2. Public Health Agency of Canada.  Hepatitis C Fact Sheet.  Retrieved April 4, 2008 from http://www.phac-aspc.gc.ca/hcai-iamss/bbp-pts/hepatitis/hep_c-eng.php
3. Public Health Agency of Canada.  Hepatitis C in Canada.  CCDR 2001; 27S3:13-15.
4. Wong T, Lee S.  Hepatitis C: A review for primary care physicians.  CMAJ.  2006; 174:649-659.
5. Public Health Agency of Canada. I-track : enhanced Surveillance of Risk Behaviours among People who Inject Drugs. Phase 1 report, August 2006. Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, 2006. http://www.phac-aspc.gc.ca/i-track/sr-re-1/index-eng.php.
6. Strathdee SA, Patrick DM, Currie SL et al. Needle exchange is not enough: lessons from Vancouver injecting drug use study. AIDS, 1997. Jul;11(8):F59-65
7. Bruneau J, Lamothe F, Franco E, et al. High rates of HIV infection among injection drug users participating in needle exchange programs in Montreal: results of a cohort study. Am J Epidemiol, 1997; 146(12): 994-1002.
8. Archibald CP, Ofner M, Patrick DM et al. Needle exchange program attracts high-risk injection drug users. XI International Conference on AIDS. Vancouver, July 1996 [abstract TuC320]

Acknowledgements

I-Track is possible as a result of collaboration between the Public Health Agency of Canada and researchers, provincial and local health authorities and community based organisations from participating sites across Canada; coordination is provided by the Surveillance and Risk Assessment Division, and HCV and HIV testing is performed by the National HIV and Retrovirology Laboratory. Special thanks to the I-Track study participants. Further information on I-Track may be obtained at http://www.phac-aspc.gc.ca/aids-side/about/itrack-eng.php.

For more information on Hepatitis C, please contact:

Surveillance and Epidemiology Section
Community Acquired Infections Division
Centre for Communicable Disease and Infection Control
Tunney’s Pasture
Postal Locator: 0603B
Ottawa, Ontario K1A 0K9
Fax: (613) 941-9813