HIV

HIV stands for human immunodeficiency virus. It was originally isolated in Paris in May 1983 by Luc Montagnier. It belongs to a group of viruses called retroviruses.

Retroviruses copy their genetic material into the genetic material of human cells. This means that infected cells stay infected for the rest of their lives.

Through mechanisms which are still not fully understood, HIV prevents the immune system from working properly. Normally, the body's immune system would fight off infection. But HIV is able to infect key cells (called CD4 cells) which co-ordinate the immune system's fight against infection.

Many are destroyed during the first few weeks of infection. Subsequently CD4 cells, both infected and others which are not themselves infected, as well as other parts of the immune system, no longer work properly. This is thought to be because the presence of HIV keeps the immune system in a state of over-activation which eventually drains its resources.

AIDS

AIDS stands for acquired immune deficiency syndrome. AIDS is the result of the damage to the immune system caused by HIV.

A damaged immune system is unable to protect the body against certain specific 'opportunistic' infections and tumours. These are called opportunistic because they are caused by organisms which are normally controlled by the immune system but which 'take the opportunity' to cause disease if the immune system has been damaged.

The opportunistic infections which are considered to be 'AIDS-defining' are listed in the HIV & AIDS Treatments Directory. Unlike most other diseases, different people with AIDS may experience different clinical problems, depending on which specific opportunistic infections they develop. This is what a syndrome means – a collection of different signs and symptoms that are all part of the same underlying medical condition.