HIV/AIDS Epi Update - May 2004

HIV/AIDS Among Injecting Drug Users in Canada

Introduction

At A Glance

Injecting drug use accounts for
7.2% of cumulative adult AIDS cases and 16.7% of cumulative adult positive HIV test reports up to June 30, 2003.

The 2002 national HIV estimates of prevalence and incidence indicate that the proportion of new HIV infections among IDU has decreased slightly from 34% of the total in 1999 to 30% or 800-1600 new infections in 2002.

The estimated number of new HIV infections among IDU in 2002 remains unacceptably high.


An enhanced surveillance system (I-Track) has been initiated at selected centres across Canada to monitor HIVassociated risk behaviours, and HIV and HCV prevalence among IDU.

In the early 1980s, the Canadian HIV epidemic was concentrated among men who have sex with men (MSM). By the early to mid-1990s, there was a change toward increasing transmission among injecting drug users (IDU), and by 1999 approximately 34% of the total number of the estimated 4,190 new HIV infections that occurred in Canada that year were among IDU.¹ The Centre for Infectious Disease Prevention and Control (CIDPC) has recently published national HIV prevalence and incidence estimates for 2002.². The 2002 estimates indicate that the proportion of new infections among IDU has decreased slightly to 30% in 2002 (800-1,600 of a total 2,800-5,200 new infections). A similar trend has occurred in the number of adult positive HIV tests reported to CIDPC. Surveillance data as of June 30, 2003, indicate that in 2002, 24.0% of adult positive HIV tests reported to CIDPC were attributed to IDU, down from a peak of just over 33% in 1996 and 1997.³ This Epi Update presents information on the status of HIV/AIDS among IDU in Canada.

AIDS Surveillance Data³

Injecting Drug Use Remains a Significant Exposure Category among AIDS Cases

• As of June 30, 2003, there have been 18,934 AIDS cases reported to CIDPC since the early 1980s. Of the 18,041 cumulative adult AIDS cases with known exposure category, 7.2% (1,307) were attributed to injecting drug use and, of these, 73.4% were males. An additional 4.6% (834) were attributed to men who have sex with men and who also inject drugs (MSM/IDU).
• There was a rise in the proportion of IDU among reported adult AIDS cases from 3.3% between 1979 and 1993 to a peak of 21.5% in 1998. The proportion decreased to 14.8% in 2001 but increased to 19.1% in 2002 (Figure 1).
• The proportion of adult male AIDS cases attributed to IDU steadily increased from 3.8% in 1992 to a peak of 19.3% in 2000. This proportion was in the range of 15% to 17% in 2001-02.
• Females represent 26.5% of the total cumulative adult AIDS cases attributed to IDU for which exposure category and gender are reported. The proportion of adult female AIDS cases attributed to injecting drug use increased steadily from 18.0% in 1992 to a peak of 46.2% in 1998. This proportion dropped to 37% in 2000, and trends since then are difficult to interpret because of the small number of reported cases.

HIV Surveillance Data

Proportion of Adult HIV Positive Test Reports among IDU Continues Gradual Decline

While AIDS data provide information on HIV infections that occurred about 10 years in the past, HIV data provide a picture of more recent infections.

• Of the 26,673 cumulative positive HIV tests in adults reported to CIDPC with exposure category information since reporting began in 1985 to June 30, 2003, 16.7% were attributable to injecting drug use (69% males). An additional 2.3% were attributed to MSM/IDU.
• Figure 2 shows the proportion of adult positive HIV tests attributed to injecting drug use by year of test, to the end of 2002. This proportion has gradually decreased from 28.8% in 1999 to 24.0% in 2002.
• The proportion of positive HIV test reports in adult females that could be attributed to IDU peaked at 48.5% in 1999, declining to about 35% in 2001-02. The proportion in adult males attributable to IDU remained stable at approximately 23% in 1999-2001 and decreased slightly to 20.3% in 2002.
• Of positive HIV test reports attributed to IDU during 2001-02 that provided age information, the highest proportion was among those aged 40-49 years (27.1%), followed by those aged 30-39 years (25.8%).

Figure 1. Proportion of adult AIDS cases attributed to IDU, by year of diagnosis 1992-2002

Figure 2. Proportion of adult positive HIV test reports attributed to IDU, by year of test 1985-2002

Studies Confirm HIV Prevalence

Remains Unacceptably High at Sentinel Centres across Canada

In response to a need for ongoing monitoring of HIV prevalence and incidence rates as well as risk behaviours in IDU populations from across the country, an HIV and hepatitis C (HCV)-associated risk behaviour enhanced surveillance system (I-Track) is being established by Health Canada at sentinel centres across Canada through collaboration with provincial, regional and local health authorities, community-based organizations and researchers. A pilot study of the I-Track surveillance system was undertaken between October 2002 and March 2003 in which a total of 794 IDU were surveyed in Victoria, Regina, Sudbury and Toronto; linkages are also being made with the SurvUDI study in Quebec. Selected findings of the I-Track pilot phase4 are reported below, as well as those reported by other studies among IDU in Canada.

• Results from the I-Track pilot phase show that the HIV prevalence among the IDU study participants in Victoria was 16.0%,4 lower than the 21% prevalence rate observed in a 1999 Victoria study.⁵
• In Regina, the HIV prevalence among I-Track participants was 1.2%, slightly lower than the 2.0% reported by the Regina Seroprevalence Study involving a similar sample size of IDU in 2000.
• In Sudbury, an HIV prevalence of 10.1% was observed, and in Toronto the HIV prevalence of 5.1% was lower than the rate of 8.2% previously reported in a 1998 study in that city.⁷
• HCV prevalence rates were high at all I-Track sentinel centres and ranged from 54.3% in Toronto to 79.3% in Victoria.⁴
• The co-infection rate, in which participants are infected with both HIV and HCV, was found to be 7.8% overall in the I-Track pilot phase.⁴
• The SurvUDI study has been ongoing since 1995 and consists of centres providing needle exchange services and other prevention programs to IDU in the province of Quebec and in Ottawa, Ontario. HIV prevalence for the overall network has increased significantly from 12.2% in 1995 to 18.6% in 2002 (R Parent, Institut national de santé publique du Québec, Québec: personal communication, February 2004).Results show that HIV prevalence among study participants for the whole network from 1995 to June 30, 2003, was 14.7% and was higher in urban centres (15.7%) than semi-urban centres (6.0%). In 2002, HIV prevalence in Montreal, Ottawa and Quebec were found to be 23.3%, 19.7% and 15.9% respectively.⁸
• Results from the Winnipeg Injection Drug Epidemiology (WIDE) study suggest that the prevalence of HIV infection among IDU in that city increased from 2.3% in 1986-90 to 12.6% in 1998.⁹
• Research conducted by Calgary's Needle Exchange Program showed that the prevalence of HIV among IDU attending that city's NEP increased from 2.2% in 1992 to 3.3% in 1998.¹⁰
• Results indicate that HIV incidence among repeat service attendees in the SurvUDI network decreased significantly from 5.3 per 100 person years (PY) in 1995 to 2.6 per 100 PY in 2002. Overall incidence from 1995 to June 30, 2003, was 2.9 per 100 PY in Quebec City, 4.4 per 100 PY in Montreal, 4.8 per 100 PY in Ottawa/Hull, 1.9 per 100 PY in semi-urban sites and 3.7 for the overall SurvUDI network.⁸
• The POLARIS study investigated HIV incidence according to risk category among repeat testers in Ontario's diagnostic HIV-testing database during the period 1992-2000. HIV incidence among IDU decreased from 0.64 per 100 PY in 1992 to 0.14 per 100 PY in 2000.¹¹
• A study examining trends in HIV incidence in Ontario based on identifying recent infections among new HIV diagnoses (using the serological testing algorithm for recent HIV seroconvertors or STARHS assay) found that HIV incidence among IDU was 0.25 per 100 PY in Toronto, 0.70 per 100 PY in Ottawa and 0.15 per 100 PY elsewhere in Ontario.¹²
• Results from the Vancouver Injection Drug User Study (VIDUS) showed that HIV incidence was 1.5 per 100 PY in 2000, down from 10.3 in 1997 and 3.2 in 1999.¹³

Women, Youth and Aboriginal IDU Are Particularly at Risk of HIV Infection

Women

• Since 1996, approximately one-third to one-half of new HIV test reports among women have been attributed to injecting drug use. The latest national HIV estimates published by CIDPC for 2002 indicate that a slightly lower proportion of new HIV infections among women in 2002 were attributed to IDU than in1999 (47% versus 54% respectively).²
• Findings from the VIDUS study in Vancouver show that during the period May 1996 and December 2000, HIV incidence rates among female IDU in Vancouver were about 40% higher than those of male IDU.¹⁴

Youth

• Results from the I-Track pilot phase indicate that 30% of participants reported initiation of injecting at the age of 16 years or younger.⁴
• High HIV incidence rates were found among young IDU when the VIDUS study in Vancouver examined rates of HIV positivity among IDU participants who were 24 years of age and younger. HIV incidence rates in this age group were 2.96 among males and 5.69 among females per 100 PY,15 compared with an overall incidence rate of 1.5 per 100 PY in 2000.¹³ This study also found that among young IDU (age 13-24 years), HIV prevalence was associated with female gender, history of sexual abuse, engaging in survival sex, injecting heroin daily, injecting speedballs daily, and having numerous lifetime sexual partners.¹⁶
• The HIV incidence among street youth in the Montreal Street Youth Cohort Study was 0.69 per 100 PY as of September 2000. Injecting drug use was the strongest predictor of HIV seroconversion (becoming HIV positive).¹⁷
• The Enhanced Surveillance of Canadian Street Youth (ESCSY) is a national, multi-centre, cross-sectional surveillance system of Canadian street youth, aged 15-24, which examines sexually transmitted infections, blood-borne pathogens and risk behaviours among street youth. Results of phases II and III of ESCSY show that approximately one-fifth of street youth surveyed had injected drugs in their lifetime.¹⁸

Aboriginal

• Aboriginal persons are overrepresented in IDU populations, and a larger proportion of Aboriginal HIV and AIDS cases are attributed to IDU than non-Aboriginal cases.19 The 2002 national HIV estimates indicate that 63% of all new HIV infections among Aboriginal people in 2002 were attributable to injecting drug use, a proportion higher than the 30% attributed to IDU among new infections overall.²
• Results of the I-Track pilot phase showed that, overall, 38.6% of the study participants self-identified as being of Aboriginal ethnic background. Most of these were from Regina, where 90.2% of the study population was Aboriginal. The proportion of Aboriginal IDU among the remaining study population ranged from 11.3% in Toronto to 20.7% in Victoria.⁴
• An analysis comparing the seroconversion rates of Aboriginal IDU with those of non-Aboriginal IDU recruited between 1996 and 2000 for the VIDUS study in Vancouver found that Aboriginal IDU are seroconverting at twice the rate of non-Aboriginal IDU.²⁰

International trends

A report published by UNAIDS and the World Health Organization (WHO) in December 2003 indicates that an estimated 40 million people in the world are living with HIV/AIDS, of whom 2.5 million are children under 15 years of age. IDU is cited as one of the main modes of transmission for those living with HIV/AIDS in seven of the 10 regions of the world and include North America, North Africa and the Middle East, Western Europe, and East Asia and Pacific. In Eastern Europe and Central Asia, where the epidemic began relatively later than in other regions (early 1990s), injecting drug use is listed as the single main mode of transmission.²¹ Figure 3 shows the proportion of AIDS cases attributed to IDU in selected countries since 1995. While caution should be taken when comparing and interpreting data from surveillance systems that may differ, it is interesting to note that although Canada is in the lower half of the graph, countries like Australia, Netherlands and the UK have even lower proportions of reported AIDS cases attributed to IDU. While such ecological comparisons have their limitations, this difference may be related to the availability and acceptability of programs and services that advocate harm reduction for IDU populations in these countries. More research is needed to study the effectiveness of these programs and whether similar approaches could be applicable in the Canadian setting.

Figure 3. Proportion of reported AIDS cases attributed to IDU in selected countries by year of diagnosis

Sources (accessed January 2004)

• Public Health Agency of Canada Centre for Infectious Disease Prevention and Control
• Centers for Disease Control and Prevention (United States)
• National Center in HIV Epidemiology and Clinical Research , The University of New South Wales, Sydney, NSW
• European Center for the Epidemiological Monitoring of AIDS
• UNAIDS/WHO. Epidemiological Fact Sheets on HIV/AIDS and Sexually Transmitted Infections

Comment

A number of biases must be taken into account when interpreting the results given here.. HIV diagnostic data are limited to persons who present themselves for testing, and so trends in these numbers may be influenced by testing patterns and/or improved ability to remove duplicate tests. In addition, identifying information that accompanies HIV testing data is sometimes incomplete or inaccurate, and this may limit the usefulness of HIV data. Results of cohort studies are limited by selection biases, loss to follow-up, and problems with generalizability. Studies that have a cross-sectional design have their own respective limitations.

Despite these issues, available data show that the HIV epidemic among IDU in Canada continues to be a serious problem. Although the problem is best documented in larger cities, increasingly it is now being seen outside major urban areas. The establishment of the I-Track enhanced surveillance system represents a milestone in the objective of describing changing patterns in drug injecting and sexual behaviourss, HIV testing behaviours, and HIV and HCV prevalence among IDU in Canada. Results from the I-Track pilot phase suggest that the pattern of drug use and HIV prevalence differs markedly across Canada and within provinces. These findings highlight the importance of expanding the geographic coverage of the surveillance system and the need to include semi-urban centres in the future. Policy and programs to address drug use and HIV will need to be tailored according to local issues and IDU migration patterns.

The high levels of risky injecting and sexual behaviours reported by IDU in sentinel sites across Canada suggest that the potential for the transmission of HIV in these populations continues to be significant. Given the geographic mobility of IDU and their social and sexual interaction with non-users, the dual problem of injecting drug use and HIV infection is one that ultimately affects all of Canadian society.

References

1. Health Canada. Archibald CP, Remis RS, Farley J, Sutherland D.
   Estimating HIV prevalence and incidence at the national level: combining direct and indirect methods with Monte-Carlo simulation.
   XII International Conference on AIDS, Geneva, June-July 1998 (Abstract 43475).
2. Geduld J, Gatali M, Remis RS, Archibald CP.
   Estimates of HIV prevalence and incidence in Canada, 2002. CCDR 2003;29(23)197-206.
3. Health Canada. HIV and AIDS in Canada: surveillance report to June 30,2003.
   Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Health Canada, November 2003
4. Health Canada.
   I-Track: enhanced surveillance of risk behaviours among injecting drug users in Canada. Pilot survey report. Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Health Canada, 2004.
5. Poffenroth L.
   RARE Project in Victoria. Proceedings of the Division of HIV/AIDS Epidemiology and Surveillance Annual Meeting, Halifax, November 16-18, 2000. Centre for Infectious Disease Prevention and Control, Health Canada.
6. Regina Health District, Saskatchewan Health, Division of HIV/AIDS Epidemiology and Surveillance, CIDPC, Health Canada.
   The Regina Sero-prevalence Study: a profile of injection drug use in a Prairie city. 2000.
7. Millson P, Myers T, Calzavara L et al.
   Regional variation in HIV prevalence and risk behaviours in Ontario injection drug users (IDU). Can J Public Health 2003;94(6):431-35.
8. Parent R, Alary M, Morrissette C et al. and the SurvUDI working group.
   Rapport SurvUDI 2003. Dec 2003.
9. Elliot LJ, Blanchard JF, Dinner KI et al.
   The Winnipeg Injection Drug Epidemiology (WIDE) Study. Eighth Annual Canadian Conference on AIDS, Vancouver BC May 1-4 1999. Can J Infect Dis 1999;10(suppl B):C314.
10. Guenter DC, Fonseca K, Nielsen DM et al.
    HIV prevalence remains low among Calgary's Needle Exchange Program participants. Can. J Public Health. 2000;91(2)129-132.
11. Burchell A, Calzavara LM, Major C et al. and the Polaris Study Team.
    HIV incidence among persons undergoing repeat diagnostic HIV testing in Ontario, 1992-2000. Can J Infect Dis 2002;13(Suppl A):48A (Abstract 315).
12. Remis RS, Major C, Swantee C et al.
    Trends in HIV incidence in Ontario based on the detuned assay: update to December 2002. Presentation at Ontario HIV Treatment Network, 5th Annual Research Day, Toronto, Ontario, November 3-4, 2003.
13. Tyndall M, Johnston C, Craib K et al.
    HIV incidence and mortality among injection drug users in Vancouver - 1996-2000.
    Can J Infect 2001;11(Suppl B):69B 354P.
14. Spittal PM, Craib KJP, Wood E et al.
    Risk factors for elevated HIV incidence rates among female injection drug users in Vancouver. Can Med Assoc J 2002;166(7)894-99.
    

[Back] [Table of Contents] [Next]