Published in the B.C. Medical Journal 1995, 37(10):702-704

Current Trends in the Epidemiology of HIV/AIDS in British Columbia

Strathdee SA; Hogg RS; Schechter MT.

Introduction:

Recent reports indicate that the rate of newly reported AIDS cases in Canada has continued to increase for the last two years.¹ The most recent estimate of the cumulative number of HIV-1 infections in Canada is 42,500 to 45,000.² British Columbia has consistently accounted for 18-20% of all reported AIDS cases in Canada,³ and it is estimated that at least 6000 persons are currently living with HIV in this province.⁴ With these facts in mind, it is crucial that we continue to monitor trends in the epidemiology of HIV-1 infection in this province and develop mechanisms for measuring the impact of future public health interventions.

In this review, we will highlight current knowledge of the HIV/AIDS epidemic in British Columbia, focusing on AIDS surveillance data and studies of HIV-1-related mortality, prevalence and incidence among sub populations at high risk of infection.

AIDS Case Surveillance:

At the end of the first quarter of 1995, a total of 1969 AIDS cases had been reported in British Columbia,⁵ and 11,192 in Canada.⁶ The cumulative incidence rate, which refers to the total number of AIDS cases reported thus far per million Canadians, is currently 398 cases per million, but is higher in British Columbia.³ Although AIDS case data are limited by under-reporting, reporting delay, under diagnosis, and changes to the case definition, these data are the single most commonly cited piece of information pertaining to the HIV-1 epidemic and are crucial for the allocation of resources for medical care, evaluating the impact of public health interventions, monitoring the changing spectrum of AIDS-related conditions in Canada, and performing trend analysis and back-calculations.

It is worthwhile to note a number of recent changes to the case definition of AIDS have impacted the extent to which AIDS cases accurately reflect trends in the epidemic. In the United States, the Centers for Disease Control and Prevention (CDC) included pulmonary tuberculosis, recurrent bacterial pneumonias, and invasive cervical cancer in the CDC case definition of AIDS, effective January, 1993.⁷ In addition, the CDC now considers that HIV-1 infection concomitant with a CD4 cell count of less than 200 per mm³, or less than 14% of the total lymphocyte count qualifies for an AIDS diagnosis. In 1994, Canada revised the national AIDS case definition by adopting the three new indicator diseases described above, but not the criterion concerning CD4 counts below 200 mm.⁸ Acceptance of the CD4 criterion would have increased the AIDS case load by 75-80%.⁹ Therefore, differences in the AIDS case definitions in the US and Canada need to be taken into account when comparing the burden in these two countries.

Trends in AIDS Mortality Rates:

Approximately 70% of all reported AIDS cases in Canada⁶ and 76.9% of those reported in B.C. are deceased.⁵ Recent analyses of HIV/AIDS related mortality revealed that HIV/AIDS was the leading cause of premature mortality in adult males in Vancouver, Montreal and Toronto from 1989-1992,¹⁰ as indicated by person-years of life lost (PYLL). On a national level, male PYLL attributable to HIV/AIDS more than doubled between the period from 1987 to 1991.^10,11 More recently, it was shown that HIV-related mortality rates differed by region and gender. Sex-specific mortality rates were significantly higher than the Canadian average in British Columbia, Quebec, and Ontario for men and in Quebec for women.¹² Overall, B.C. accounted for 17% of all deaths attributable to HIV/AIDS between 1987 and 1992. It should also be acknowledged that AIDS-related mortality are under-estimated by at least 10-20%,¹³ and trends in mortality are also influenced by factors related to access to diagnostic and treatment expertise and must be interpreted accordingly.

Trends in HIV Prevalence and Incidence:

In a previous report³ we discussed characteristics of the HIV epidemic among homosexual/bisexual men, and studies of HIV seroprevalence conducted from serum samples of women of child-bearing age and the general population. The following discussion focuses on current information on other populations identified to be at high risk, that is injection drug users (IDUs) and their sexual partners and prison populations.

Injection Drug Users:

There is a growing urgency surrounding the rapid spread of HIV-1 among IDU populations in Canada. For example, the cumulative incidence rate of HIV-1 infection among IDUs attending a needle exchange Montreal was 9.8 per 100 person-years over the four-year period between 1989 and 1993, which is among the highest in North America.¹⁴ Although HIV incidence data is lacking from other provinces, it is evident that HIV-1 prevalence rates among IDU populations vary widely by region. For example, following a period of relatively stable seroprevalence rate in 1991 and 1992 in Toronto where HIV-1 prevalence was 4.5% and 4.8% respectively,¹⁵ prevalence rose to 7.6% during the period from 1993 to 1994.¹⁶ This trend was partially attributed to higher infection rates among male IDUs who reported having sex with other males. In contrast, Calgary and Winnipeg have reported rates of 1.9%¹⁷ and 2.3%¹⁸ respectively. Given the disparity in these HIV prevalence rates across the country, an understanding of migration patterns will be necessary if appropriate interventions are to be developed.

 

In British Columbia, the prevalence of street-involved IDUs appeared relatively stable between 1988 and 1992, with an overall prevalence of 3.2%.¹⁹ However, a large increase in the number of IDUs testing HIV-positive has prompted a case-control investigation.²⁰ A noticeable increase in the number of HIV-positive IDUs attending a Vancouver-based clinic specializing in HIV-infection has also been documented in the province.²¹ Although no recent estimates of HIV-1 prevalence are available, HIV testing data suggests that the proportion of IDUs testing HIV-positive in the province has risen from approximately 1% in 1987-1988 to 5.4% by the end of 1994.²² During this same period, persons with mixed risk profiles (e.g. homosexual/bisexual men who report IDU and female sex trade workers reporting IDU) also increased appreciably. Although the generalizability of these data are limited because of bias introduced by self-referral for HIV testing, the dramatic increase in the proportion of IDUs testing HIV-positive is cause for concern.

 

A more detailed investigation conducted by the B.C. Centre for Disease Control indicated that 75% of seropositive tests occurring between August and December, 1994, were among males;²² however, the proportionate increase among female IDUs was equally alarming. Female IDUs are also at risk of infection through sexual contact with other IDUs, and many street-involved IDUs also engage in commercial sex work. Since it is well known that sex trade workers are less likely to consistently use condoms with their regular sexual partners than with their clients, health promotion campaigns which are geared towards increasing condom use and lowering the risk of sexually transmitted diseases and HIV are needed.

 

At present, the majority of HIV-positive tests appears to be concentrated within the Downtown Eastside of Vancouver, an area which is reknowned for its poverty, homelessness and ethnic diversity. At the time of writing, the increase among IDUs testing HIV-positive in the province showed no signs of achieving a plateau. Since it is well recognized that HIV incidence rates among IDUs may double or triple within a one year period,²³ curtailing the spread of infection within this community remains an urgent priority.

Prison Populations:

Generally speaking, HIV-1 prevalence rates among incarcerated populations are often directly related to the proportion of inmates who report IDU.²⁴ A voluntary HIV-1 seroprevalence study of adults in BC provincial prisons in 1993 found HIV prevalence rates of 3.3% among women and 1.0% among men. The higher rate of infection among women was attributed to the fact that IDUs were over-represented among incarcerated females. These results are consistent with reports from other provinces.^25,26

 

In 1994, a similar study conducted among juveniles aged 12 to 19 detained in BC correctional facilities reported an overall HIV-1 prevalence of 0.25%.²⁷ This relatively low HIV prevalence rate should not be interpreted as being reassuring, since this study also demonstrated that patterns of high risk behaviour began early, and specific behaviours such as IDU were equally common among older versus younger youth. Female young offenders aged 16-19 were five times more likely to have engaged in IDU than same aged males. In addition, female youth were more likely to have had sex with an IDU partner than males, which suggests that this group is at particularly high risk for infection with HIV and other STDs. The potential for HIV transmission within provincial and federal prisons, is also of concern, since there is no access to sterile injection equipment in these facilities despite the widespread use of drugs. Thus, there remains an urgent need for harm reduction programs for inmates which are coordinated with the communities to which they will return.

Summary:

HIV testing data suggests that there has been a dramatic increase in the number of IDUs testing HIV-positive in British Columbia. New interventions and further research is needed to determine HIV prevalence and incidence in this population. Given the current situation among IDUs in Canada, the potential for increased heterosexual and perinatal transmission is also of concern. Future research which focuses on other marginalized populations such as prisoners and ethnocultural communities is also needed, especially among urban and rural Aboriginal communities. For each thousand new HIV-1 infections, approximately $100 million is added to our collective future direct medical costs²⁸ and approximately $0.6 billion in indirect costs, primarily through lost productivity.²⁹ By the end of 1994, it was estimated that at least 6000 individuals are living with HIV-1 in this province and more than 1300 have died;⁴ we cannot expect the burden of HIV/AIDS to lessen in the near future.

Acknowledgements:

The authors are supported by the National Health Research Development Program of the Department of Health, Canada, through a National Health Research Scientist Award granted to Dr. Schechter and a postdoctoral fellowship granted to Dr. Strathdee. We gratefully acknowledge Drs. Michael O'Shaughnessy, Julio S.G. Montaner and Michael Rekart for critical appraisal of the manuscript, and Ms. Elizabeth Ferris for secretarial support.

REFERENCES

For more information, contact:

Bonnie Devlin
Vanguard Project Coordinator
608 - 1081 Burrard Street
Vancouver, BC, Canada, V6Z 1Y6
Tel: (604)806-8306
Fax: (604)806-9044