Final Report: Estimating the Number of Persons co-infected with Hepatitis C Virus and Human Immunodeficiency Virus in Canada

3.3 HCV-HIV co-infection in Canada, as of December 1999

3.3.1 HCV-HIV co-infection by exposure category and geographic region

The final results of the analysis indicating the estimated number of HCV-HIV co-infected persons in Canada are shown in Tables 8a and 8b. This was derived by multiplying the number of HIV-infected persons by the HCV prevalence among HIV-infected persons as presented in Table 7. As shown in Table 8a, we estimated that 11,194 persons were infected with both HCV and HIV in Canada as of December 1999. Of these, the vast majority (85%) were injection drug users, including those with and without same sex exposure. The 95% confidence limits for the estimates by exposure category and region are also shown in Table 8a; for the total number of HCV-HIV infections, they were 9,400 and 13,300.

Table 8b shows the distribution of HCV-HIV infected persons by geographic region. The vast majority (88%) of dually infected persons in Canada live in Quebec (34%), British Columbia (29%) or Ontario (25%).

3.3.2 HCV-HIV co-infection in the Aboriginal population

Estimating the extent of HIV infection among the Aboriginal population is somewhat challenging. To the best of our knowledge, no population-based studies of HIV prevalence among Aboriginals have been carried out in Canada. The problem of HIV infection in this population appears largely related to injection drug use though it may also be related to some extent to heterosexual transmission.

Overall, according to the Vancouver Injection Drug Use Study (VIDUS), approximately 20% of injection drug users in Vancouver are Aboriginal. There is probably an over-representation of Aboriginal persons, especially men, among IDUs in Vancouver and other major cities of western Canada, though less in Toronto and Montreal. If, overall, the Aboriginal population represents about 10% of the injection drug using population in Canada, a reasonable estimate of the number of Aboriginal injection drug users would be 8,000. Since the Aboriginal population of Canada is estimated at 800,000, this means that approximately 1% of this population are injection drug users, a plausible proportion. If HIV prevalence among Aboriginal injection drug users were estimated to be approximately 15%, the number of HIV-infected IDUs of Aboriginal ethnicity in Canada would be approximately 1,200.

Tables 9 through 11 summarize the results of the estimates of dual HCV-HIV infection for the Aboriginal population. Table 9 presents the results of the review of published studies among IDUs and MSM, including persons of Aboriginal status, indicating observed and HIV and HCV prevalences <6-9 >. Table 10 shows the number of HIV-infected Aboriginal persons by exposure category; these estimates were provided by Health Canada as noted above.

The final results of the analysis on HCV-HIV co-infection among Aboriginal persons, as of December 1999 are shown in Tables 11a and 11b. In all, we estimate that there are 1,477 persons with HCVHIV dual infection among the Aboriginal population, with a 95% plausible range of 1,030 to 2090. Of the 1,477 co-infected Aboriginal persons, 87% are among heterosexual injection drug users, and approximately 10% are among men who both inject and have sex with other men. These two groups together account for 97% of co-infected persons in this population. As shown in Table 11b, the largest number of dually infected Aboriginal persons resides in British Columbia, representing alone 56% of such persons in Canada.

3.3.3 HCV-HIV co-infection among prisoners

We estimated the number of HIV-infected persons in prisons in a preliminary fashion. The majority of incarcerated persons co-infected with HIV and HCV almost certainly acquired their infections through injection drug use.

According to Correctional Service Canada, the population incarcerated in federal institutions as of 1996 was approximately 13,800. Of these, approximately 30% had ever injected drugs, and 10% had injected drugs within the year previous to their incarceration. Overall, based on estimates carried out in the Consortium to characterize injection drug use in Canada (CCIC) study <50> and HIV prevalence studies, we estimate that the federal prison population infected with HIV is likely to be approximately 410 persons. This estimate was derived by multiplying 13,800 by 30% (number of IDUs) and by 10%, (the estimated HIV prevalence among injection drug users). Correctional Service Canada reports that 196 prisoners in federal institutions were known to be HIV-infected as of December 1999 <51>. The observation that only about 50% of HIV-infected prisoners would be known to prison authorities is plausible since not all HIV-infected persons have been diagnosed and some persons who have been diagnosed would not divulge this information to prison authorities.

The detailed analysis of HCV prevalence among prisoners in both federal and provincial institutions is presented in Tables 12 through 14. Table 12 presents the results of a review of risk factors for HIV and HCV infection and HIV and HCV infection rates summarized from published studies <12-23, 52-4>. The proportion of prisoners with a history of drug injection varied from 12% to 52%. Past history of injection drug use was consistently higher in female prisoners than in male prisoners. A history of injection was 50% higher in the two studies where both sexes were examined. Nevertheless, women represent a minority of prisoners in most provinces, generally in the range of 5% to 15% of prison populations.

The observed prevalence of HIV among IDU prisoners varied widely, from 1% to 15%. HIV prevalence was generally higher in women. Among non-IDUs, HIV prevalence was markedly lower, and with few exceptions, 1% or lower. The crude HIV prevalence in men or mixed populations observed in nine studies carried out in Ontario, Quebec and British Columbia from 1989 to 1998 varied from 1% to 4%.

Table 13 presents the number of prisoners by province and the proportion estimated in each exposure category by province.

Tables 14a and 14b presents the results of our analysis of dual HCV-HIV infection among prisoners. As seen in Table 14a, we estimate that, among the persons incarcerated as of December 1999, 611 persons incarcerated in Canadian prisons were co-infected with HCV and HIV. Of these, 88% were injection drug users, and 11% were male injection drug users who also had sex with other men. Together, these account for 99% of co-infections among prisoners. The 95% plausible limits for the number of co-infected prisoners were 420 to 870 persons.

As seen in Table 14b, the largest number of HCV-HIV co-infections were (in descending order) in Ontario, Quebec and British Columbia, accounting for 28%, 23% and 22%, respectively, for a combined total of 72% of co-infected prisoners in Canada.

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