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 paper provides a description of persons who have been diagnosed with HIV and AIDS up to 30 June 2004 and reported up to 7 weeks after this date by all provinces and territories to the Centre for Infectious Disease Prevention and Control (CIDPC). 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 of positive HIV tests and AIDS diagnoses from all provincial and territories to CIDPC.
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 (who comes forward for testing). In addition, surveillance data can only tell us about persons who have been tested and given a diagnosis of HIV or AIDS 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 be diagnosed until later years.
It is important to be cautious when interpreting the surveillance data for the first half of the reporting year because of small sample sizes and delayed and underreporting. CIDPC will continue to monitor the surveillance data and will clarify whether these findings are sustained when the full year has been reported.
HIV surveillance data
A total of 56,523 positive HIV tests have been reported to CIDPC from November 1985 (when reporting began) up to 30 June 2004. The rising trend in positive test reports outlined in previous reports appears to be continuing. The annual number of reports has increased from 2,112 in 2000 to 2,499 in 2003. In addition, in the first 6 months of 2004, there were 155 more positive HIV tests reported compared with the first 6 months of 2003.
Females represent a growing proportion of positive HIV test reports, reaching 26.6% in the first half of 2004. This increasing trend is being observed particularly among younger women who represented 42.6% of the 15-29-year age group and 23.9% of the 30-39-year age group in the first 6 months of 2004 (Figure 1).
Men who have sex with men continue to represent the largest number and proportion of positive HIV tests reports. Injecting drug use was the second exposure category up until 1998, showing a peak over 33% in 1996 and 1997 and decreasing to 18% in 2003 and the first 6 months of 2004. Starting in 1999, the heterosexual category became the second largest exposure category, increasing from 7.5% prior to 1995 and reaching over 30% by 2001 (Figure 2). Within the heterosexual category, positive test reports attributed to persons from HIV-endemic countries have increased from 2.9% in 1998 to 8.6% in the first 6 months of 2004. The subcategory for those with no further risk information than heterosexual sex has also increased over time, from 2.4% before 1995 to 10.9% in the first 6 months of 2004.
It is important to note the limitations associated with AIDS diagnoses reported in the first half of 2004. No data were available from Quebec and could therefore not be included in the national summary. For this reason, annual trends in this section as well as figures for reported AIDS diagnoses are limited to data to the end of 2003.
A total of 19,468 AIDS diagnoses have been reported to CIDPC up to 30 June 2004. The proportion of females among reported AIDS diagnoses has increased from 6.1% during the period between 1979 and 1994 to 25.2% in 2003. This increasing trend is being seen particularly in the 15-29 year age group, in which female youth represented 9.8% of all AIDS diagnoses in this group prior to 1994 and 41.0% in 2003.
Men who have sex with men represent the largest exposure category among cumulative AIDS diagnoses, but annual trends demonstrate a decreasing proportion, from 78.0% prior to 1994 to 34.6% in 2003 (Figure 3). The combined heterosexual exposure category, however, has increased from 10.6% to 44.7% during the same period with the largest increases in the sub-categories origin from an HIV-endemic country and heterosexual sex as the only known risk (NIR HET).
As outlined in Figure 4, White Canadians represent a decreasing proportion of AIDS diagnoses, from 86.4% prior to 1994 to 53.8% in 2003. This decline has been coupled with increases among both Black and Aboriginal Canadians. Black Canadians represented 8.3% of diagnoses before 1994 and 20.7% among Aboriginal Canadians in 2003; during the same period the proportion among Aboriginal Canadians increased from 1.3% to 14.4% (Figure 4).
Some of the reasons for the increase in positive HIV test reports may be changes in HIV testing patterns, reporting delays, and/or underlying infection rates. However, this increase is at least in part due to changes in immigration policies at Citizenship and Immigration Canada(2) that were implemented in 2002. These changes include the addition of HIV testing to the routine immigration medical assessment and reduced restrictions on certain groups of immigrants (such as family class and refugees) who would have previously been considered medically inadmissible because of excessive demands on the Canadian health care system.
From January 2002 to 30 June 2004, 772 individuals tested positive for HIV infection during their routine immigration medical assessment in Canada (Dr. S. Martin. Acting Director, Immigration Health Program Elaboration, Medical Services Branch, Citizenship and Immigration Canada: personal communication, 2004), accounting for 12% of the positive HIV test reports during this period (note that this excludes HIV-positive applicants who apply from outside Canada). Those applicants who test positive in Canada are included in the national surveillance numbers, since they are handled in the same manner as all other positive HIV tests and included in provincial/territorial HIV reporting to CIDPC. These new policies may also be contributing to some of the changes observed in the distribution of positive test reports in exposure category and ethnic category in both HIV and AIDS surveillance.
Another important finding that will have implications for guiding prevention and treatment programs is the continuing rising trend in the proportion of positive HIV test reports among females in each age group. This is especially true among those in the younger age groups, who are soon going to represent half of the positive test reports among all young Canadians.
Public Health Agency of Canada. HIV and AIDS in Canada. Surveillance Report to June 30, 2004. Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, 2004.
Citizenship and Immigration Canada. Immigrant and Refugee Protection Act. Statutes of Canada 2001. Chapter 27. Also available at URL: <http://www.cic.gc.ca/>.
Source: J Geduld, MHSc, BSc, Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada.