For health professionals: HIV and AIDS

The Public Health Agency of Canada recently conducted a study on HIV transmission between sexual partners. Learn more about this study.

Get detailed information on the human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) for health professionals.

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What health professionals need to know about HIV and AIDS

HIV is a sexually transmitted and blood-borne infection. AIDS is a long-term sequelae of infection.

It is recommended that the consideration and discussion of HIV testing be made a component of periodic routine medical care. Early diagnosis and initiation of highly active antiretroviral therapy (HAART) can lead to reduced morbidity and mortality associated with:

  • HIV infection
  • disease progression to AIDS

Timely awareness of serostatus can reduce HIV transmission due to reductions in risk behaviour. In addition, access to HAART reduces infectiousness: people who adhere to HAART and have an undetectable viral load have a negligible risk of transmitting the infection.

Health care providers are strongly encouraged to:

  • follow the guiding principles of the HIV screening and testing guide
  • tailor testing approaches to:
    • meet the needs of their patients
    • reduce barriers to HIV testing


Pre-exposure prophylaxis (PrEP)

Pre-exposure prophylaxis (PrEP) refers to the use of prescription antiretroviral (ARV) medication by people who are HIV negative but at high risk for HIV infection, in order to lower their chances of becoming infected with HIV.

Taken before exposure, the medicine interrupts HIV's ability to copy itself in the body and prevents it from establishing an infection. The iPrEx and Partners PrEP studies showed that taking PrEP daily reduces the risk of getting sexually transmitted HIV by more than 90%Footnote 1 Footnote 2 . Participants in these trials had regular HIV and STI testing, treatment for STIs, and were given condoms. While PrEP is highly effective when taken every day, it is less effective when not taken consistently. Using condoms and other prevention methods along with PrEP can lower the risk of sexually acquired HIV even further.

In 2016, Health Canada granted market authorization of ARV (Emtricitabine 200 mg and Tenofovir Disoproxil Fumarate 300 mg) for PrEP. Individuals should consult a health care professional for more information on PrEP.

Care providers are strongly encouraged to consult with an infectious disease specialist or a colleague experienced in HIV care, to help guide the patient assessment to determine whether a benefit exists to initiate pre-exposure prophylaxis.

Post-exposure prophylaxis (PEP) following recent exposure

PEP should be initiated as soon as possible, as it may be less effective if initiated more than 72 hours after exposure.
In the event a patient presents soon after a high-risk exposure, care providers are strongly encouraged to:

  • consult with an infectious disease specialist, or a colleague experienced in HIV care
  • help guide the patient assessment to determine whether a benefit exists to initiate PEP

The decision to initiate PEP for HIV infection is based on clinical judgment and should be made jointly with the exposed individual.

Natural history and disease progression

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

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

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

  • opportunistic infections
  • primary neurologic disease
  • malignancy

Due to advances in HIV treatment:

  • the progression of the disease has slowed to a great degree
  • HIV infection is now considered a chronic, manageable condition

Clinical manifestations

Depending on the stage of infection, an individual infected with HIV may be asymptomatic or may present with non-specific symptoms that may:

  • not be recognized as an HIV infection
  • present with various signs and symptoms related to immunodeficiency (refer to the following stages for more information)

Primary acute infection

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

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

Due to the high risk of transmission at this stage, clinicians should maintain a high index of suspicion in individuals with:

  • a non-specific febrile illness and/or
  • a history of high-risk behaviour

If present, symptoms:

  • generally appear 2 to 6 weeks after exposure
  • are usually self-limited
  • generally last 1 to 2 weeks, although some may last several months
  • are similar to those of many other illnesses, including viral syndromes, such as:
    • influenza
    • mononucleosis

The symptoms of acute retroviral syndrome include:

  • fever
  • myalgia
  • arthralgia
  • sore throat
  • headache
  • rash
  • nausea
  • diarrhea
  • vomiting

Chronic asymptomatic infection

In this stage:

  • viral replication and plasma viremia are more controlled by the immune response represented by the level of CD4+ T cells.
  • generalized lymphadenopathy is frequently present
  • thrombocytopenia may be present
  • there is a decreased risk of transmission

Many HIV-infected individuals fall into this category.

Chronic symptomatic infection

In this stage, the disease is characterized by:

  • high levels of:
    • viral replication
    • plasma viremia
    • increased risk of transmission
  • a depressed CD4+ T cell count
  • viral shedding from mucosal sites

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


Many different types of HIV screening tests are licensed for use in Canada. Type and availability can vary by jurisdiction.

Approach to testing

An assessment that the individual understands how HIV is transmitted, the implications of testing (advantages and disadvantages), and how to interpret the test results is sufficient for offering an HIV test. An HIV test can be offered without in-depth behaviour-based risk assessments and/or extensive pre- and post-test counselling.

The detection of the HIV antibody is the most widely used means of diagnosing HIV.

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

  • is highly infectious but
  • tests negative on HIV antibody screening because antibodies are not immediately produced or detectable

The length of the window period varies with the test used. Of the 2 main types of tests:

  1. third-generation HIV enzyme immunoassay (EIA) antibody tests:
    • are able to detect the antibody in 99% of people 3 months after exposure
    • may detect the antibody as early as 20 to 30 days after exposure in some individuals.
  2. fourth-generation combination tests:
    • also permit the detection of p24 antigen during the acute phase of infection
    • reduce the window period to between 15 and 20 days

HIV infection can also be diagnosed by detecting the presence of the virus itself.

  • qualitative viral detection tests (NAAT), and/or quantitative NAAT (viral load testing) can be used under certain circumstances.
  • genotyping and phenotyping are also used for monitoring HIV drug resistance


Advances in HIV treatment:

  • have slowed disease progression to such a degree that HIV infection is now understood to be a chronic, manageable condition
  • are enabling more people with HIV to live healthy, long and active lives

Early diagnosis and initiation of HAART can lead to reduced morbidity and mortality associated with HIV infection and disease progression.

Treatment of HIV is a rapidly evolving and complex area, with changes in optimal therapy occurring as new research/evidence becomes available.

If HAART is being considered, consultation with a colleague experienced in HIV/AIDS care or infectious diseases is recommended.

Your local public health authority will have a listing of these health professionals.

It is important to note that effective treatment with HAART can be an important prevention strategy. Effective treatment reduces infectiousness: people who adhere to HAART and have an undetectable viral load have a negligible risk of transmitting the infection.


Health professionals in Canada play a critical role in identifying and reporting cases of HIV/AIDS. Refer to the surveillance section for more information on surveillance in Canada.


Footnote 1

Grant RM, Lama JR, Anderson PL, McMahan V, Liu AY, Vargas L, et al. Preexposure Chemoprophylaxis for HIV Prevention in Men Who Have Sex with Men. N Engl J Med 2010;363 (27):2587-99.

Return to footnote 1 referrer

Footnote 2

Baeten J, Donnell D, Ndase P, Mugo N, Campbell J, Wangisi J, et al. Antiretroviral prophylaxis for HIV prevention in heterosexual men and women. N Engl J Med 2012;367 (5):399-410.

Return to footnote 2 referrer

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