At a glance: HIV/AIDS surveillance to 31 December, 2003

Introduction

HIV and AIDS surveillance data are presented regularly in a semi-annual report HIV and AIDS in Canada published each April and November. The following article provides a description of persons who have been given a diagnosis of HIV and AIDS up to 31 December, 2003, and whose diagnosis has been reported to the Centre for Infectious Disease Prevention and Control (CIPDC) up to 7 weeks after this date by all provinces and territories. Further details, including a series of tables and technical details, are available in the most recent surveillance report(1). Surveillance of HIV and AIDS in Canada is ongoing thanks to the voluntary reporting to CIDPC of positive HIV tests and AIDS diagnoses from all provinces and territories.

Surveillance data understate the magnitude of the HIV epidemic and consequently do not represent the number of people infected with HIV (prevalence) or the number infected each year (incidence). Some of the reasons for this include the fact that surveillance data are subject to delays in reporting, underreporting and changing patterns in HIV testing behaviours (i.e. who comes forward for testing). In addition, surveillance data can tell us only about persons who have been tested and whose HIV or AIDS has been diagnosed, and not those who remain untested and undiagnosed. Furthermore, because HIV is a chronic infection with a long latent period, many persons who are newly infected in a given year may not receive a diagnosis until later years.

CIDPC has recently produced estimates of HIV prevalence to the end of 2002 and HIV incidence in 2002(2). These estimates were produced using a combination of methods and incorporating data from a wide variety of sources, including HIV test reports, AIDS case reports, population-based surveys, targeted epidemiologic studies and census data. It was estimated that at the end of 2002 there were approximately 56 000 (46 000- 66 000) people in Canada living with HIV (including those living with AIDS), and for approximately one-third of these the condition was undiagnosed. The number of people in Canada newly infected with HIV in 2002 was estimated to be 2800 to 5200.

HIV Surveillance Data

There have been 55 180 positive HIV tests reported to CIDPC since HIV testing began in 1985. The annual number has declined from 2996 in 1995 to 2187 in 2001 and has since increased to 2504 in 2002 and 2482 in 2003. The increase in the number of positive HIV test reports in the last 2 years may be partly attributed to recent changes in immigration policies at Citizenship and Immigration Canada(3). These changes include the addition, in January 2002, of HIV screening to the routine immigration medical assessment and reduced restrictions on certain groups of immigrants who would have previously been considered medically inadmissible associated with changes to the definition of some applicant groups. In most provinces and territories, for the HIV screening conducted in Canada, the positive HIV test reports are handled in the same manner as all other positive HIV tests and are included in provincial/territorial HIV reporting to CIDPC.

Females are representing a growing proportion of positive HIV test reports. For the last 3 years females have accounted for around one-quarter of positive HIV test reports with known gender; this is a rise from 8.9% during the period between 1985 and 1992. This pattern is seen in all age groups and most notably in the 15 to 29 and 30 to 39-year age groups, as seen in Figure 1.

Figure 1. Proportion of females among positive HIV test reports by age group

Proportion of females among positive HIV test reports by age group

As outlined in Figure 2, men who have sex with men (MSM) continue to account for the largest number and proportion of positive HIV test reports. This proportion decreased from close to 75% between 1985 and 1994, dropped in the mid to late 1990s and remained close to 37% until a slight increase in the last 3 years to 44.4%. The diverse heterosexual exposure category has steadily increased from 7.5% before 1995 to 36.9% in 2003. This exposure category is made up of three subcategories: heterosexual contact with a person who is either HIV-infected or at increased risk of HIV, heterosexual as the only identified risk, or origin in a country where HIV is endemic. Over the last 5 years, from 1998 to 2003, the proportion of positive HIV test reports attributed to the latter heterosexual subcategory has increased from 2.9% to 10.2%.

Figure 2. Positive HIV test reports by exposure category and year of test

Positive HIV test reports by exposure category and year of test

Aids Surveillance

There have been a cumulative 19 344 AIDS diagnoses in Canada reported to CIDPC up to the end of 2003. The annual number of reported AIDS diagnoses adjusted for reporting delay increased throughout the 1980s and early 1990s, peaking at 1953 in 1993; it then declined and has started to level off to 500 to 600 diagnoses per year. This pattern of declining AIDS diagnoses has been reported in other industrialized areas, including the United States, Australia, and the United Kingdom. The decline has been largely attributed to the widespread use of highly effective antiretroviral therapy since 1996; however, there is a growing concern that AIDS diagnoses are becoming increasingly underreported.

The largest proportion of reported AIDS cases are among those aged 30 to 44 years followed by the 45 to 59 and 15 to 29-year age groups, accounting for 60.4%, 19.4%, and 15.9% of all AIDS diagnoses respectively. Adult females increasingly represent a larger proportion of diagnosed AIDS cases. Over the last 10 years this proportion has increased from 7.0% in 1993 to 24.2% in 2003 (among AIDS diagnoses with reported age and gender). In 2003, females represented 42% of AIDS diagnoses among those aged 15 to 29 years, 25.4% among those aged 30 to 44 years and 18.2% among 45- to 59-year-olds.

Over the last decade, there has been a decrease in the proportion of reported AIDS cases among MSM, falling from 73.8% in 1993 to 35.3% in 2003. Conversely, the diverse heterosexual exposure category has shown an increase in this proportion, from 13% in 1993 to 43.8% in 2003.

The proportion of reported AIDS cases attributed to White Canadians has been decreasing over time, from 86.8% before 1993 to 54.3% in 2003. This decrease is coupled with increases seen among both Black and Aboriginal Canadians, as outlined in Figure 3. Black Canadians represented 8.4% of cases before 1993 and 21.5% in 2003; during the same period this proportion among Aboriginal Canadians increased from 1.2% to 13.4%.

Figure 3. Non-White ethnic categories as a percentage of all reported AIDS diagnoses, by year of diagnosis (all ages)

Non-White ethnic categories as a percentage of all reported AIDS diagnoses, by year of diagnosis (all ages)

Interpretation

The increasing proportion of both positive HIV test reports and AIDS diagnoses attributed to the heterosexual exposure category and the distribution in its subcategories reveal a trend that will be followed and further analyzed in the coming months. The rising proportion of positive HIV test reports among Aboriginal and Black Canadians as well as among females in each age group, especially in the younger years, is an important finding that has implications for guiding prevention and treatment programs.

Acknowledgements

National level HIV and AIDS surveillance is possible as a result of all provinces and territories participating in, and setting directions for, HIV and AIDS surveillance. Accordingly, CIDPC acknowledges the provincial/territorial HIV/AIDS coordinators, laboratories, health care providers and reporting physicians for providing the non-nominal confidential data that enable this report to be published. Without their close collaboration and participation in HIV and AIDS surveillance, the publication of these data would not have been possible.

References

  1. Health Canada. HIV and AIDS in Canada. Surveillance report to December 31, 2003. Ottawa: Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Health Canada, 2003.

  2. Geduld J, Gatali M, Remis RS et al. Estimates of HIV prevalence and incidence in Canada, 2002. CCDR 2003;29:197-206.

  3. Citizenship and Immigration Canada. Immigrant and Refugee Protection Act. Statutes of Canada 2001. Chapter 27.

Source: J Geduld, MHSc, BSc, Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Health Canada.


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