HIV

HIV stands for human immunodeficiency virus. It was identified in the early 1980s and it belongs to a group of viruses called retroviruses.

Normally, the body's immune system would fight off an infection, but HIV prevents the body’s immune system from working properly. HIV infects key cells in the body’s natural defences called CD4 cells, which co-ordinate the body’s response to infection. Many CD4 cells are destroyed by being infected, and some stop working as they should.

Although HIV can't be cured, it can be treated. Modern HIV treatment means that many people with HIV are living long, healthy lives and can look forward to a near-normal lifespan.

AIDS

If HIV isn't treated, the gradual weakening of the immune system leaves the body vulnerable to serious infections and cancers which it would normally be able to fight off. These are called ‘opportunistic infections’ because they take the opportunity of the body’s weakened immunity to take hold.

If someone with HIV develops certain opportunistic infections, they are diagnosed as having AIDS. The term 'AIDS' stands for acquired immune deficiency syndrome. People diagnosed as having AIDS can become unwell with a range of different illnesses, depending on the specific opportunistic infections they develop. This is why AIDS is not considered a disease, but a syndrome – a collection of different symptoms and illnesses, all caused by the same virus, HIV.

Most people who have HIV have not had an AIDS diagnosis. Also, if someone develops an AIDS-defining illness this doesn't mean that they are on a one-way path to illness and death. Thanks to HIV treatment, many people who were once diagnosed as having AIDS are now living long and healthy lives.