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HIV & AIDS glossary

word cloud of HIV related terms


Adherence means taking HIV treatment exactly as you are advised to by your healthcare professional (including time of day, frequency, with or without food, and so on). Poor adherence can lead to drug resistance which means your treatment will stop working. It’s particularly important to make sure you don’t run out of drugs, as a break in treatment is damaging.


AIDS stands for Acquired Immune Deficiency Syndrome and is a set of symptoms and illnesses that occur at the very final stage of HIV infection. It’s diagnosed when someone’s immune system is severely damaged, and can no longer fight off infections. AIDS and HIV are not the same.

Antiretroviral drugs (ARVs)

ARVs are drugs used to treat HIV and prevent it from replicating in the body. Antiretrovirals keep the virus at a low level in the body, improve the health of the immune system, and reduce the likelihood of passing HIV on. Effective treatment can reduce the virus to undetectable levels.

Antiretroviral treatment (ART)

ART is the treatment for HIV – a combination of three or more antiretroviral drugs that target different stages of the HIV lifecycle.

CD4 count

Your CD4 count is an indication of how healthy your immune system is - it should go up when you have HIV treatment. It’s the number of CD4 cells (or T-helper cells) in your blood which is measured by a simple blood test. It’s often talked about at the same time as viral load (the concentration of HIV in your blood): generally when your CD4 count is high, your viral load is low and vice versa.


Chemsex describes the sex that gay men have when using certain drugs. It can involve groups (including larger party settings), couples or lone masturbation.


Voluntary medical male circumcision (VMMC) reduces female-to-male sexual transmission of HIV by 60%. VMMC as an HIV prevention tool is recommended by the World Health Organization and UNAIDS in countries with a high HIV prevalence among the general population – primarily East and Southern Africa.


Co-infection is when someone has more than one serious infection 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, but also more important.


Comorbidity 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.


When a person shares their HIV status, they’re telling someone that they’re HIV positive. (Though the word 'disclosure' has been used for a long time in this context, there is now an emphasis on using the words 'sharing' or 'telling'. This is because 'disclosing' can often reinforce stigmatising beliefs that a person has done something wrong if they are living with HIV.) 

Drug resistance

If someone with HIV doesn’t take their antiretroviral treatment properly, the drugs may become unable to control the virus which can cause the treatment to stop working – this is called drug resistance. It’s also possible for someone who has developed a drug-resistant strain of HIV to pass it on.

External condom (male condom)

An external condom is a thin piece of rubbery material that fits over a man’s penis during sex, forming a barrier to protect against sexually transmitted infections (STIs) including HIV, and unplanned pregnancy.

False negative result

A false negative result is when a person has HIV but an HIV test shows that they don’t have it. A false negative result usually happens during the window period immediately after initial infection, before current tests are able to detect it.

False positive result

A false positive result is when a person does not have HIV but an HIV test shows that they do. Whenever someone receives a positive test result, they are tested again to confirm the result.

First-line treatment

First-line treatment is the initial antiretroviral treatment recommended for HIV – it’s a combination of three or more antiretroviral drugs from two different drug classes.


HIV stands for Human Immunodeficiency Virus. It attacks a person’s immune system cells, and if left untreated severely damages their immune system and their ability to fight off infections.

HIV cure

There is no cure for HIV, although antiretroviral treatment can control the virus, meaning that people with HIV can live long and healthy lives.

HIV vaccine

There isn’t a vaccine for HIV though a number of HIV vaccine trials show encouraging results.

Internal condom (female condom)

An internal condom is a thin pouch that can be inserted into the vagina or anus before sex, forming a barrier to protect against sexually transmitted infections (STIs) including HIV, and unplanned pregnancy.


m-health is defined by the World Health Organization as the use of mobile devices – such as mobile phones, patient monitoring devices, personal digital assistants and wireless devices – for medical and public health practice.3

Mixed-status couple

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

Post-exposure Prophylaxis (PEP)

PEP is short-term treatment that must be taken within 72 hours of possible exposure to HIV, for example, after unprotected sex. It stops HIV spreading throughout the body.

Pre-exposure Prophylaxis (PrEP)

PrEP is a daily course of antiretroviral drugs that can prevent HIV infection. It’s for men and women who do not have HIV but who may be at higher risk of HIV infection because they have an HIV-positive partner, or are unable to negotiate condom use, or are having repeated sex without a condom. When PrEP is adhered to exactly as prescribed, it eliminates the risk of HIV infection. But if doses are missed then the risk of infection increases substantially.

Opportunistic infection

Opportunistic infections are a type of infection that occur in people with a weakened immune system (for example people living with HIV).

Second-line treatment

When first-line antiretroviral drugs stop working, a person takes second-line treatment.


HIV self-testing offers the convenience of taking a test in the comfort of your own home or other private place. These kits are becoming more widely available and give a result in 15 to 20 minutes.


syndemic or synergistic epidemic is the combination of two or more coexisting epidemics in a population, for example HIV and TB. Biological interactions between the coexisting epidemics make the prognosis and burden of disease worse.  

Sexually transmitted infection (STI)

STIs are infections that are passed on during sexual contact. Examples include chlamydia, genital herpes, gonorrhoea, hepatitis C and trichomoniasis. HIV is also a sexually transmitted infection although there are other ways it can be passed on.

T-helper cells

See CD4 count above.

Third-line treatment

When second-line drugs stop working, a person takes third-line treatment.

Undetectable / virally suppressed

A person living with HIV is considered to have an ‘undetectable’ viral load – or to be virally suppressed – when antiretroviral treatment has brought the level of virus in their body to such low levels that blood tests cannot detect it. As long as treatment is adhered to and a person’s viral load remains undetectable (as monitored by a health professional), they can’t pass HIV on to others through sex, and their health is not affected by the virus.

Viral load

A person’s viral load is the amount of HIV virus in their blood. It is measured by a simple blood test. It indicates how well a person’s antiretroviral treatment is working.

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. This is between 2 and 12 weeks depending on the type of test.

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Last full review: 
08 October 2018
Next full review: 
08 October 2019
Last updated:
01 July 2019
Last full review:
08 October 2018
Next full review:
08 October 2019