HIV-1 Strain and Primary Drug Resistance in Canada

Surveillance Report to June 30, 2001

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HIV-1 Subtypes in Canada

National HIV Reference Services

The provincial public health laboratories, the Canadian Blood Services, and HEMA-QUEBEC test thousands of samples each year and thus serve as crucial partners in the CHSDRSP. A number of factors can cause serologic tests to yield fallible results. These include samples from seroconverters, samples that are cross- reactive, for example to HIV-2 and divergent strains of HIV-1. Furthermore, genetic variants of HIV can be problematic for HIV PCR and viral load tests, often leading to discordant findings with serologic testing.

As a part of its reference services, the National HIV Laboratories test samples showing unusual serologic, PCR or other virologic test results. This function of the National HIV Laboratories is crucial in addressing one of the goals of the CHSDRSP - protection of the blood supply - since screening tests should be able to detect all circulating strains of HIV within Canada. This relationship between the provincial and national laboratories may also serve in quality assurance and diagnostic kit monitoring.

As of June 30, 2001, the National Laboratory for HIV Genetics has analyzed serologic samples from five provinces, submitted through the reference services, for subtype. The results of these analyses are shown in Table 9.

HIV-2

There is currently no active surveillance for HIV-2 in Canada. At the time of writing this report (December 31, 2001), a total of six samples submitted to the National Laboratory for HIV Reference Services had been identified as belonging to HIV type 2. This number is likely to be an underestimate: it is possible that HIV-2 cases have been reported as HIV-1 because the only approved HIV western blot kit is specific to HIV-1. Discussions are currently under way to enhance surveillance for HIV-2.

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