Medical Terms

AIDS (Acquired immunodeficiency syndrome): the most advanced stage of HIV infection, AIDS is a collection of specific illnesses and conditions which occur because the body’s immune system has been damaged by HIV.

Antiretroviral therapy (ART): antiretroviral drugs and therapies are used in the treatment of retroviruses, primarily the human immunodeficiency virus (HIV).

Adherence: taking medications or treatment exactly as prescribed (not missing doses, taking doses at the right time, taking the correct amount, and following any instructions about food). The benefits of strict adherence to an HIV regimen include sustained viral suppression, reduced risk of drug resistance, improved overall health and wellbeing, and decreased risk of HIV transmission.

CD4 Cells: the primary white blood cells of the immune system which signal to other immune system cells how and when to fight infections. HIV weakens the immune system by destroying CD4 cells (also known as T cells or T helper cells).

CD4 Cell Count or CD4 Count: a laboratory test that measures the number of CD4 cells in a sample of blood and reflects the state of the immune system. In people living with HIV, the CD4 count is the most important laboratory indicator of immune function and the strongest predictor of HIV progression. The CD4 count is also used to monitor a person’s response to antiretroviral therapy (ART). The CD4 cell count of a person who is HIV negative can be anything between 500 and 1500. When the CD4 count of an adult falls below 200, there is a high risk of opportunistic infections and serious illness.

Effective treatment: the treatment effect is the additional benefit provided by the treatment.  Effective treatment for HIV is used to describe suppression of the virus to an undetectable level so that there is zero risk of passing the virus on to others.

HIV (Human immunodeficiency virus): the virus that causes AIDS, HIV is a retrovirus transmitted through direct contact with HIV-infected body fluids (blood, semen, vaginal or rectal fluids, or breast milk). There are two variants or subtypes: HIV-1 (the most common worldwide) and HIV-2.

HIV medication: see Antiretroviral Therapy.

HIV status: HIV positive or HIV negative.

HIV transmission: the transfer of a disease or infection from person to person. HIV is transmitted mainly by having condomless sex or sharing drug injection equipment with someone who is HIV positive. HIV can be also passed from mother to child during pregnancy, labour or delivery, or breastfeeding (through breast milk).

HIV treatment: see Antiretroviral Therapy.

Late HIV diagnosis: defined as a CD4 cell count less than 350 cells/ul or an AIDS-defining illness at diagnosis. Late diagnosis of HIV is associated with a ten-fold increase in the risk of short-term mortality (within a year of diagnosis) and an increased risk of the onward transmission of HIV.

Newly diagnosed: the number of people who have received an HIV diagnosis regardless of when HIV was first acquired. Individuals may have been living with HIV for many years before receiving a positive diagnosis.

Post-exposure prophylaxis (PEP): HIV PEP is a short-term antiretroviral preventive treatment to reduce the likelihood of HIV infection after potential exposure.

Pre-exposure prophylaxis (PrEP): a medication taken before exposure or possible exposure to HIV to prevent the acquisition of HIV.

Transfer of care: moving one’s HIV medical care to a new jurisdiction or country.

Treatment as Prevention (TasP): A term that describes the prompt provision of antiretroviral treatment in people with HIV to lower a person’s viral load to undetectable levels to reduce the risk of HIV being transmitted to others.

U=U: stands for Undetectable = Untransmittable and means that when a person living with HIV is on regular treatment which lowers the amount of virus in his or her body to undetectable levels, there is zero risk of passing on HIV to others. The low level of virus is described as an undetectable viral load.

Undetectable viral load: when the amount of the virus (HIV) is too low to be detected by the viral load test. An undetectable viral load is the primary goal of antiretroviral therapy.

Untransmittable: zero risk of passing on HIV to another person.

Viral load: measurement of the amount of virus (HIV) in a sample of blood.  Viral load is reported as the number of HIV RNA copies per millilitre of blood plasma (e.g. 50 copies/ml). Viral load is an important indicator of HIV progression and how well treatment is working.

Viral suppression: halting of the function or replication of a virus.  With HIV, optimal viral suppression is when antiretroviral therapy reduces a person’s viral load to an undetectable level.