You are here

HIV & AIDS glossary


Adherence means taking HIV treatment exactly as you were told to. Poor adherence can lead to drug resistance which means the treatment will stop working.


AIDS stands for Acquired Immune Deficiency Syndrome and is caused by the HIV virus. It is diagnosed when a person’s immune system is too weak to fight off infections.

Antiretroviral drugs (ARVs)

These are drugs used to treat HIV and prevent it from copying itself and spreading throughout the body. They keep the virus at low levels.

Antiretroviral treatment (ART)

This is the treatment for HIV. ART uses a combination of three or more antiretroviral drugs (ARVs) to stop HIV from spreading throughout the body.

CD4 count

CD4 count is a measure of the number of CD4 cells (or T-helper cells) in a sample of blood. A simple blood test can count the cells. CD4 cells are a type of immune system cell in the body that HIV attacks and kills over time.


This is when someone has more than one health condition at the same time. For example, when a person with HIV also has tuberculosis (TB), they are said to have an HIV/TB co-infection. This can make treatment for both infections more difficult.


This describes someone who has two or more diseases or health conditions at a time. For example, a person with HIV may also have high blood pressure.

Drug resistance

If someone with HIV doesn’t take their treatment properly, the drugs may become unable to control the virus which can cause the treatment to fail.

False negative result

When a person has HIV but is diagnosed as not having it, it's called a false negative result. For example, a false negative HIV test indicates a person does not have HIV, when in fact, they do.

False positive result

When a person does not have HIV but is diagnosed as having it, it's known as a false positive result. For example, a false positive HIV test indicates a person has HIV when actually they don’t.

First-line treatment

The recommended treatment for HIV that is made up of three or more antiretroviral drugs is known as first-line treatment.


HIV stands for Human Immunodeficiency Virus. It attacks a person’s immune system cells, and without treatment, can lead to AIDS.

Post-exposure Prophylaxis (PEP)

PEP is short-term treatment that must be taken straight after possible exposure to HIV, for example after unprotected sex. It stops HIV spreading throughout the body and causing an infection.

Pre-exposure Prophylaxis (PrEP)

PrEP is a course of treatment taken before possible exposure to HIV to reduce the risk of infection.

Opportunistic infection

This is a type of infection that occurs in people with a weakened immune system (for example people living with HIV).

Second-line treatment

A course of antiretroviral drugs that is taken if first-line treatment has failed is called second-line treatment.

Serodiscordant couple

A serodiscordant couple is when one person has HIV and the other does not. Also known as a discordant couple, a serodifferent couple, or a mixed-status couple.

Sexually transmitted infection (STI)

STIs are infections that are passed on during sexual contact. Examples include chlamydia, gonorrhoea and trichomoniasis.

Third-line treatment

A course of antiretroviral drugs that is taken if second-line treatment has failed is called third-line treatment.

Viral load

Viral load is the amount of virus in the blood. It is measured by a simple blood test.

Window period

The time between HIV infection and when the body produces enough HIV antibodies to be detected by an HIV test is called the window period.

Photo credit: Copyright AVERT

Last full review: 
01 May 2015

Would you like to comment on this page?

We are unable to respond to any questions, or offer advice or information in relation to personal matters.

By submitting this form, you accept the Mollom privacy policy.
Last updated:
29 July 2016
Last full review:
01 May 2015