Monitoring the ultimate HIV indicator: prevalence and incidence at the national level in Canada
Q. Yang1, D. Boulos2, P. Yan1, F. Zhang1, R. Remis3, D. Schanzer1, C. Archibald1
1Public Health Agency of Canada, Ottawa, Canada, 2Department of National Defence, Ottawa, Canada, 3University of Toronto, Toronto, Canada
Background: Estimates of national HIV prevalence and incidence can help to effectively monitor the HIV epidemic at the national level and to guide and evaluate prevention programs.
Methods: We used multiple methods to estimate national HIV prevalence and incidence in Canada in 2008, including a workbook method (multiplying the estimated prevalence or incidence rate by the estimated population size), two statistical modelling methods (back-calculation of HIV incidence by relating the timing of HIV positive testing with timing of HIV infection and testing behaviour), and an iterative spreadsheet model which incorporates elements of the other methods. These methods were used for the six Canadian provinces representing ~98% of HIV cases and interpolated for the remaining provinces and territories.
Results: The number of people living in Canada with HIV infection (including AIDS) continues to increase, from an estimated 57,000 in 2005 to 65,000 in 2008. Nearly half (48%) were men who have sex with men (MSM), 22% were women, and 8% were of Aboriginal ethnicity. Approximately 16,900 (26%) of prevalent cases were unaware of their HIV infection, including 6,000 MSM, 2,800 injecting drug users (IDU), and 7,000 non-IDU heterosexuals. An estimated 2,300 to 4,300 incident infections occurred in Canada in 2008, essentially unchanged from the 2005 estimate of 2,200-4,200. Among new infections, 26% were women and 13% were Aboriginal persons. MSM comprised 44%, IDU 17%, heterosexuals born in high prevalence countries (mainly sub-Saharan Africa/Caribbean) 16%, and other heterosexuals 20%.
Conclusions: HIV incidence in Canada is not decreasing and prevalence is increasing ~4.5% per year. Aboriginal persons and persons from high prevalence countries continue to be over-represented in Canada´s HIV epidemic. Although these estimates are necessarily imprecise (especially for incidence), they are useful for planning and evaluating HIV prevention and care programs and focussing attention on the need for key additional data.
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