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Acquired Immunodeficiency Syndrome (AIDS) including Human Immunodeficiency Virus (HIV)

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Reporting Obligations

Laboratory confirmed cases of HIV infection shall be reported to the local Health Unit.

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Aetiologic Agent

The human immunodeficiency virus (HIV) is a retrovirus of which two types have been identified: type 1 (HIV-1) and type 2 (HIV-2). They are serologically and geographically distinct but have similar epidemiological characteristics.

Clinical Presentation

HIV – As the virus that causes AIDS, early testing, diagnosis and treatment for HIV are important factors in reducing morbidity and mortality associated with HIV infection and disease progression to AIDS. Depending on the stage of infection, an individual infected with HIV may be asymptomatic or may present with non-specific symptoms. Due to the high risk of transmission of HIV during the primary acute infection stage, clinicians should maintain a high index of awareness in individuals with a non-specific febrile illness and/or a history of high-risk behaviour.

HIV infection can generally be broken down into three distinct stages: primary acute infection, chronic asymptomatic stage, and chronic symptomatic infection, before progression from HIV to AIDS.

Primary acute infection: Symptoms, if present (fever, arthralgia, myalgia, rash, sore throat, fatigue, headache, oral ulcers and/or genital ulcers, weight loss, nausea, vomiting or diarrhea) generally appear two to six weeks after exposure, are usually self-limited, and last one to two weeks, although some may last several months.

Chronic asymptomatic infection: Individuals may be free of clinical signs or symptoms, though generalized lymphadenopathy and/or thrombocytopenia may be present. Disease progression varies but can last years.

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

AIDS – AIDS is a severe, life threatening clinical condition and an advanced HIV-related disease. This syndrome represents the late clinical stage of HIV infection resulting from progressive damage to the immune system, leading to one or more opportunistic infections and cancers of which bacterial pneumonia is one of the common presentations.

Modes of Transmission

Person to person transmission through: unprotected sexual intercourse; contact with infected body fluids such as sexual fluids (vaginal, seminal and anal), blood, and breast milk; cerebral spinal fluid (CSF); the use of HIV-contaminated needles and syringes and some drug paraphernalia, including sharing by injection drug users; transfusion of infected blood or its components; organ and tissue transplants; mother to child transmission; and contact of abraded skin or mucosa with body secretions such as blood, CSF or semen.

Incubation Period

Variable; time from initial infection to detectable antibodies varies depending on the test that is used. The time from HIV infection to diagnosis of AIDS has an observed range of less than one year to 15 years or longer.

Period of Communicability

Begins early after onset of HIV infection, highlighting the importance of treatment to reduce communicability. Infectivity during the early stages is considered to be high; it increases with viral load, with worsening clinical status and with the presence of other sexually transmitted infections (STIs). Advances in HIV treatment have slowed disease progression to the degree that HIV infection is now understood to be a chronic, manageable condition, in which people can live healthy, long and active lives. Early diagnosis and initiation of treatment can lead to reduced communicability associated with HIV infection and disease progression.

Risk Factors/Susceptibility

Presumed to be general; race, sex and pregnancy status do not appear to affect susceptibility to HIV infection or AIDS. The presence of other STIs especially if ulcerative increases susceptibility.

Diagnosis and Laboratory Testing

The diagnosis of HIV infection is based primarily on a positive serologic test. Persons with HIV infection may be totally asymptomatic. Therefore, serologic testing is recommended when there is a high index of suspicion (e.g., high-risk behaviour and/or suspicious clinical symptoms and signs). Persons may also present with specific opportunistic infections or other conditions indicative of underlying immunosuppression. See ‘Public Health Ontario Labstract May 2016, HIV patient information sheet: If You’ve Just Found Out You Are HIV Positive’.

Ontario HIV Testing Guidelines

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Treatment and Case Management

The Public Health Agency of Canada provides information related to: screening, testing, post-test procedures, post-diagnosis clinical management and disclosure of HIV. As well, ‘Clinical Care Guidelines for Adults and Adolescents Living with HIV in Ontario, Canada’ was released in February, 2017 to establish standards of care for people with HIV and to strengthen HIV care delivery by building needed capacity and better care coordination.

Patient Information

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Additional Resources

OHTN HIV Clinical Guidelines Working Group, “Clinical care guidelines for adults and adolescents living with HIV in Ontario, Canada, February 2017.”

Public Health Agency of Canada, “Human Immunodeficiency Virus – HIV Screening & Testing Guide.” – “Canada’s source for HIV and hepatitis C information.”

Canadian AIDS Society publication. “HIV Transmission: Facts that Affect Biological Risk, 2013.”

AMMI Canada position statement: The use of early antiretroviral therapy in HIV-infected persons | Journal of the Association of Medical Microbiology and Infectious Disease Canada (


LGLDHU Sexual Health Clinic Information Page


Ministry of Health and Long-Term Care, Infectious Diseases Protocol, 2022.

Heymann, D.I., Control of Communicable Disease Manual (19th Ed.), Washington, American Public Health Association, 2008.