HIV in Canada Among Persons from Countries where HIV is Endemic

Appendix B Exposure category hierarchy

Exposure Category Hierarchy

HIV and AIDS cases are assigned to a single exposure category according to a hierarchy of risk factors. If more than one risk factor is reported, a case is classified as the exposure category listed first (or highest) in the hierarchy. For example, injecting drug users (IDU) may also be at risk of HIV infection through heterosexual activity. Injecting drug use is accepted as the higher risk activity even though there may also be risk of HIV infection through sexual activity. The only exception to this is men who are reported to have had sex with men (MSM) and to have also injected drugs. Such cases are classified in the combined exposure category MSM/IDU.

Exposure Categories

The exposure categories are defined as follows:

MSM: Men who have had sex with men; this includes men who report either homosexual or bisexual contact.

MSM/IDU: Men who have had sex with men and have injected drugs.

IDU: Injecting drug users. Blood/Blood Products:

1. Recipient of Blood/Clotting Factor: Before 1998, it was not possible to separate this exposure category. However, where possible, it has been separated into subcategories b and c.

2. Recipient of Blood: Received transfusion of whole blood or blood components, such as packed red cells, plasma, platelets or cryoprecipitate.

3. Recipient of Clotting Factor:Received pooled concentrates of clotting factor VIII or IX for treatment of hemophilia/coagulation disorder.

Heterosexual Contact

1. Origin from an HIV-Endemic Country/ Sexual Contact with a Person at Risk: Before 1998, it was not always possible to separate this exposure category. However, where possible, it has been separated into subcategories b and c.

2. Origin from an HIV-Endemic Country: People who were born in a country where HIV is endemic (i.e. a country in which the predominant means of HIV transmission is heterosexual contact).

3. Sexual Contact with a Person at Risk: People who report heterosexual contact with someone who is either HIV-infected or who is at increased risk for HIV infection (i.e. injecting drug user, bisexual male, or a person from an HIV-endemic country).

4. NIR-HET: If heterosexual contact is the only risk factor reported and nothing is known about the HIV-related factors associated with the partner, the case would be classified as No Identified Risk-Heterosexual (NIR - HET).

Occupational Exposure: Exposure to HIV contaminated blood or body fluids, or concentrated virus in an occupational setting. This applies only to reported AIDS cases and not occupational positive HIV test reports, which are listed under “Other”.

Perinatal Transmission: The transmission of HIV from an HIV-infected mother to her child either in utero, during childbirth, or through breastfeeding.

Other: Used to classify cases in which the mode of HIV transmission is known but cannot be classified into any of the major exposure categories listed here - for example, a recipient of semen from an HIV positive donor.

NIR (No Identified Risk): Where the history of exposure to HIV through any of the modes listed is unknown, or there is no reported history. This exposure category may include cases that are currently being followed up by local health department officials; people whose exposure history is incomplete because they died, declined to be interviewed or were lost to follow-up; and people who cannot identify any mode of transmission.

Exposure Category Not Reported: In certain provinces, it is not possible to report information regarding exposure category; such cases are thus classified as Not reported. This applies only to positive HIV test reports, and not to reported AIDS cases.

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