HIV-1 Strain and Primary Drug Resistance in Canada
Surveillance Report to June 30, 2002

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Information to the readers of HIV-1 Strain and Primary Drug Resistance in Canada

The Division of HIV/AIDS Epidemiology and Surveillance and the national HIV laboratories at the Centre for Infectious Disease Prevention and Control, Health Canada, are pleased to provide you with the HIV-1 Strain and Primary Drug Resistance in Canada: Surveillance Report to June 30, 2002. Primary drug resistance is a term used to identify resistance observed in HIV-infected individuals who have never before received treatment and so presumably have been infected with a drug-resistant strain of HIV.

This report presents data that are shared by the provinces/territories participating in the Canadian HIV Strain and Drug Resistance Surveillance Program. The Division of HIV/AIDS Epidemiology and Surveillance is responsible for data management, data analyses, and writing and coordination of the publication of this report. The Division of Retrovirus Surveillance is responsible for coordinating the collection of the HIV data. The National Laboratory for HIV Genetics is responsible for conducting the subtyping and drug resistance genotyping.

The major finding in this surveillance report is that primary drug resistance to antiretroviral drugs has been identified in 7.1% of our sample population of 847 treatment naVve individuals. Resistance to more than one class of antiretroviral drug has been identified in 0.7% of the sample population. For the first time, we report primary drug resistance to non-nucleoside reverse transcriptase inhibitors. Primary drug resistance has been observed in females and males; across different age groups, ethnicities, and exposure categories; in HIV-1 subtype A, B, and C infections; and in recent and prevalent HIV infections. With respect to HIV-1 subtypes, subtype B continues to predominate in Canada, 93.1% of the samples belonging to this group, but HIV-1 subtypes A, C, D, and E and the recombinant subtypes A/B, A/C, and A/G have been identified across Canada. Significantly higher proportions of non-B infections were detected among females (compared with males), among people reporting heterosexual contact as their primary exposure factor, and among people of Black, Asian or mixed ethnicities. There is geographic variation in the prevalence of non-B HIV-1 subtypes, and this variation is likely related to travel and migration from countries where other subtypes predominate.

From a public health perspective, while primary drug resistance may not yet be a significant problem in Canada, it will no doubt play a significant role in shaping the course of the HIV epidemic in this country and worldwide. For this reason, the data from the Canadian HIV Strain and Drug Resistance Surveillance Program will be valuable to guide Canada's response to the public health problems posed by drug-resistant HIV, including our efforts to develop treatment strategies and effective prevention programs. The introduction of variant HIV-1 subtypes into Canada also requires vigilant monitoring in order to ensure that diagnostic and screening algorithms can adequately detect all circulating strains and to inform vaccine research and development.

This is the second report of results from the Canadian HIV Strain and Drug Resistance Surveillance Program. We will be working towards improving this report to reflect changes in the surveillance of HIV strains and drug resistance. We welcome and appreciate your comments and suggestions.

Yours sincerely,

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