HIV and AIDS: For health professionals

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What health professionals need to know about HIV and AIDS

The human immunodeficiency virus (HIV) is a sexually transmitted and blood-borne infection (STBBI) that can be transmitted through exposure to the blood, semen, vaginal fluid, rectal fluid and human milk from a person with HIV. Perinatal transmission can also occur during pregnancy or birth.

Acquired immune deficiency syndrome (AIDS) is a long-term sequela of HIV infection.

Consider and discuss HIV testing as part of routine care. Early diagnosis and initiation of antiretroviral therapy (ART) can lead to reduced morbidity and mortality associated with HIV infection and progression to AIDS.

Individuals who are aware of their serostatus are more likely to use effective strategies to prevent HIV transmission. In addition, ART reduces transmission. People who adhere to ART and who achieve and maintain an undetectable viral load have effectively no risk of transmitting HIV sexually.


Pre-exposure prophylaxis (PrEP)

Pre-exposure prophylaxis (PrEP) is the use of prescription antiretroviral (ARV) medication by people who are HIV-negative, but at high risk for HIV infection. PrEP is used in combination with other prevention strategies to lower the risk of HIV acquisition.

Taken before exposure, the ARV medication interrupts HIV's ability to copy itself in the body and prevents it from establishing an infection.

PrEP is highly effective when taken correctly. Using condoms and other prevention methods along with PrEP can also reduce the acquisition or transmission of other STBBI.

Health professionals should consult with an infectious disease specialist or a colleague experienced in HIV care to help:

Refer to the Health Canada regulatory decision summary for approved indications, benefits and risks related to PrEP.

Post-exposure prophylaxis (PEP)

Post-exposure prophylaxis (PEP) is the use of prescription ARV medication by people who are HIV-negative to lower the risk of HIV acquisition following a high-risk exposure. PEP should be started as soon as possible and within 72 hours of exposure.

Health professionals should consult an infectious disease specialist or a colleague experienced in HIV care to help:

Treatment as prevention (TasP)

HIV treatment can also prevent transmission. People living with HIV who adhere to ART and who achieve and maintain an undetectable viral load have effectively no risk of transmitting HIV sexually.

Treatment as prevention (TasP) is an important prevention strategy. Discuss the benefits of ART as part of routine HIV care.

Progression of HIV infection

The amount of time from initial infection to the development of clinical manifestations is highly variable, as is infection progression.

HIV infection results in the progressive destruction of CD4+ T lymphocytes. These white blood cells are crucial to the normal function of the immune system.

Consequently, people with HIV and subsequent immune suppression are at risk of developing a variety of AIDS-defining conditions, including:

Due to advances in HIV treatment:

Clinical manifestations

Depending on the stage of infection, people with HIV may be asymptomatic or may present with:

Primary acute infection

This is the period from initial infection to development of the full serum antibody profile (seroconversion).

Up to 90% of people in the acute infection stage are symptomatic.

Health professionals should remain vigilant, as misdiagnosis of acute infection is common and there is a high risk of transmission at this stage. Health professionals should include HIV infection in the differential diagnosis and test for HIV when someone presents with a:

If present, symptoms:

The symptoms of acute retroviral syndrome include:

Chronic asymptomatic infection

In this stage of infection:

Many individuals living with HIV are within this stage of infection.

Chronic symptomatic infection

In this stage, the infection is characterized by:

Viral replication depletes the CD4+ T cells to the level of profound immunosuppression, leading to opportunistic infections.


Different types of HIV screening tests are licensed for use in Canada. Type and availability can vary by jurisdiction. Information on HIV screening and testing can be found in the HIV Screening and Testing Guide and Approach to HIV Screening factsheet.

Approach to testing

Health professionals should offer screening for sexually transmitted and blood-borne infections (STBBI), including HIV, as part of their clinical prevention and control strategies.

Before offering an HIV screening test, conduct an assessment and ensure the individual understands:

Normalizing screening can reduce barriers to screening and testing, and the stigma associated with HIV.

An HIV screening test can be offered without in-depth behaviour-based risk assessment and/or extensive pre- and post-test counselling.

Standard HIV Testing

In Canada, all laboratories performing HIV screening use fourth generation HIV tests, also known as combination tests, which detect both HIV antibodies and the HIV p24 antigen. These screening tests perform better in acute infection than those that only detect antibodies because the p24 antigen is detectable earlier than antibodies. With fourth generation screening tests, some people will have a reactive (positive) result as early as 15 to 20 days after HIV exposure. While most people will have an accurate test result three to six weeks after exposure, for a small number of people the window can be up to 12 weeks. If an HIV screening test indicates a reactive result, the laboratory will conduct specialized confirmatory testing to ensure correct diagnosis of an HIV infection.

In certain circumstances, qualitative nucleic amplification tests (NAAT) and/or quantitative NAAT (viral load testing) can be used to detect the virus itself. Genotyping and phenotyping are used to detect and monitor HIV drug resistance.

Rapid HIV Testing

Rapid HIV test kits licensed in Canada for point-of-care (POC) testing or self-testing require a few drops of blood from a finger prick and provide results within several minutes. Because rapid screening tests are third generation tests that only detect HIV antibodies, they generally have a longer window period than standard fourth generation HIV screening tests. While some people may have a reactive result as early as 20 to 30 days after HIV exposure, the window period can be up to 12 weeks. Reactive results are considered “preliminary” and should be confirmed with standard laboratory testing for the diagnosis of HIV infection.

Where available, rapid HIV test kits for point-of-care (POC) or self-testing can facilitate uptake of screening. In addition, rapid HIV testing provides an option for people who face barriers accessing testing in healthcare settings.

The window period is the time after acquisition of HIV, when the:


Advances in HIV treatment:

Early diagnosis and treatment can lead to reduced morbidity and mortality associated with HIV and infection progression.

Treatment of HIV infection is a rapidly evolving and complex area, with changes in recommended regimens occurring as new research and evidence becomes available. If ART is being considered, consult a colleague experienced in HIV care or an infectious diseases specialist. Local public health authorities will have a listing of these health professionals.

Effective ART can be an important prevention strategy. People who adhere to ART and who achieve and maintain an undetectable viral load have effectively no risk of transmitting HIV sexually. Effective ART can also help prevent perinatal transmission of HIV.

Undetectable = Untransmittable (U = U)

U = U reflects the scientific evidence that someone who is being treated for HIV and who achieves and maintains an undetectable viral load has effectively no risk of transmitting HIV sexually. Refer to the U = U for health professionals factsheet.

Health professionals should encourage the consistent and correct use of condoms to prevent the acquisition or transmission of other STBBI.

Health professionals should:


Health professionals in Canada play a critical role in identifying and reporting cases of HIV and AIDS.

People living with HIV in Canada

At the end of 2018, the estimated number of persons living with HIV in Canada was 62,050 (plausible range 54,600 – 70,500).

An estimated 1 in 8 Canadians who has HIV hasn’t been diagnosed and is unaware of the infection.

In the same year, an estimated 2,242 new HIV infections occurred in Canada (plausible range: 1,080 – 3,850).

People living with HIV around the world

The World Health Organization's Global Health Observatory provides data on HIV and AIDS around the world. It estimates that about 38 million people were living with HIV at the end of 2019.

Surveillance of HIV and AIDS

HIV and AIDS are both nationally notifiable diseases. National notification is voluntary and data are reported by provincial or territorial public health authorities.

Provinces and territories have legislation for the reporting of priority infectious diseases within their jurisdictions. All provinces and territories collect data on diagnosed HIV infections and report to the Public Health Agency of Canada annually. However, not all provinces and territories have mandatory reporting of AIDS.

Provinces and territories report cases to the Public Health Agency of Canada if they meet the national case definition for HIV or AIDS.

The Public Health Agency of Canada, in partnership with provinces and territories, regional and/or local public health partners, coordinates the Tracks enhanced surveillance system at sentinel sites across Canada. The Tracks system monitors trends in the prevalence of HIV and hepatitis C and associated risk factors in key populations.

Related links

Awareness resources


Canada Communicable Disease Report


External resources

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