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What are HIV and AIDS?

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What is HIV?

HIV is a virus that gradually attacks the immune system, which is our body’s natural defence against illness. If a person becomes infected with HIV, they will find it harder to fight off infections and diseases. The virus destroys a type of white blood cell called a T-helper cell and makes copies of itself inside them. T-helper cells are also referred to as CD4 cells.1

There are many different strains of HIV – someone who is infected may carry various different strains in their body. These are classified into types, with lots of groups and subtypes. The two main types are:

  • HIV-1: the most common type found worldwide
  • HIV-2: this is found mainly in Western Africa, with some cases in India and Europe.

Basic facts about HIV

  • HIV stands for human immunodeficiency virus.
  • If left untreated, it can take around 10 to 15 years for AIDS to develop, which is when HIV has severely damaged the immune system.
  • With early diagnosis and effective antiretroviral treatment, people with HIV can live a normal, healthy life.
  • HIV is found in the following body fluids of an infected person: semen, blood, vaginal and anal fluids and breast milk.
  • HIV cannot be transmitted through sweat, saliva or urine.
  • According to UK statistics, the most common way for someone to become infected with HIV is by having anal or vaginal sex without a condom.2
  • You can also risk infection by using infected needles, syringes or other drug-taking equipment (blood transmission), or from mother-to-child during pregnancy, birth or breastfeeding.3

What is AIDS?

AIDS is a syndrome caused by the HIV virus.4 It is when a person’s immune system is too weak to fight off many infections, and develops when the HIV infection is very advanced. This is the last stage of HIV infection where the body can no longer defend itself and may develop various diseases, infections and if left untreated, death.

There is currently no cure for HIV or AIDS. However, with the right treatment and support, people can live long and healthy lives with HIV. To do this, it is especially important to take treatment correctly and deal with any possible side-effects.

Basic facts about AIDS

  • AIDS stands for acquired immune deficiency syndrome.
  • AIDS is also referred to as advanced HIV infection or late-stage HIV.
  • Someone with AIDS may develop a wide range of other health conditions including: pneumonia, thrush, fungal infections, TB, toxoplasmosis and cytomegalovirus. 
  • There is also an increased risk of developing other life-limiting conditions, including cancer and brain illnesses. 
  • CD4 count refers to the number of T-helper cells in a cubic millilitre of blood. When a person’s CD4 count drops below 200 cells per millilitre of blood, they are said to have AIDS.5

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Page last reviewed: 
01 May 2015
Next review date: 
01 November 2016

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