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What are HIV and AIDS?

What is HIV?


  • HIV is a virus that attacks the immune system, our body’s natural defence against illness.
  • If HIV is left untreated, a person’s immune system will get weaker and weaker until it can no longer fight off life-threatening infections and diseases.

  • Testing regularly for HIV means you can get antiretroviral treatment if you need it and stay healthy.

  • AIDS describes a set of symptoms and illnesses that happen at the final stage of HIV infection, if left untreated.

What is HIV?

HIV is a virus that attacks cells in the immune system, which is our body’s natural defence against illness. The virus destroys a type of white blood cell in the immune system called a T-helper cell, and makes copies of itself inside these cells. T-helper cells are also referred to as CD4 cells.

As HIV destroys more CD4 cells and makes more copies of itself, it gradually weakens a person’s immune system. This means that someone who has HIV, and isn’t taking antiretroviral treatment, will find it harder and harder to fight off infections and diseases.

If HIV is left untreated, it may take up to 10 or 15 years for the immune system to be so severely damaged that it can no longer defend itself at all. However, the rate at which HIV progresses varies depending on age, general health and background.  

Basic facts about HIV

  • HIV stands for human immunodeficiency virus.
  • People with HIV can enjoy a long and healthy life by taking antiretroviral treatment which is effective and available to all.
  • Once a person has HIV, the earlier they are diagnosed, the sooner they can start treatment which means they will enjoy better health in the long term.
  • It’s possible for antiretroviral treatment to reduce the level of HIV in the body to such low levels that blood tests cannot detect it. People living with HIV whose viral load is confirmed as undetectable cannot pass on HIV.
  • Regular testing for HIV is important to know your status.
  • HIV is found in semen, blood, vaginal and anal fluids, and breastmilk.
  • HIV can’t be transmitted through sweat, saliva or urine.
  • Using external (or male) condoms or internal (or female) condoms during sex is the best way to prevent HIV and other sexually transmitted infections.
  • If you inject drugs, always use a clean needle and syringe, and never share equipment.
  • If you’re pregnant and living with HIV, the virus in your blood could pass into your baby’s body, during birth or afterwards through breastfeeding. Taking HIV treatment and becoming undetectable eliminates this risk.

What is AIDS?

AIDS is a set of symptoms (or syndrome as opposed to a virus) caused by HIV. A person is said to have AIDS when their immune system is too weak to fight off infection, and they develop certain defining symptoms and illnesses. This is the last stage of HIV, when the infection is very advanced, and if left untreated will lead to death.

Basic facts about AIDS

  • AIDS stands for acquired immune deficiency syndrome; it’s also called advanced HIV infection or late-stage HIV.
  • AIDS is a set of symptoms and illnesses that develop as a result of advanced HIV infection which has destroyed the immune system.
  • Fewer people develop AIDS now because treatment for HIV means that more people are staying well.

Although there is no cure for HIV, with the right treatment and support, people living with HIV can enjoy long and healthy lives. To do this, it’s especially important to commit to taking treatment correctly.

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Last full review: 
28 September 2018
Next full review: 
25 September 2019
Last updated:
04 March 2020
Last full review:
28 September 2018
Next full review:
25 September 2019