What is HIV?

The Human Immunodeficiency Virus (HIV) is a sexually transmitted virus (STI) that attacks the body's immune system, which provides a natural defence system against disease and infection.

HIV infects special cells, called CD4 cells, which are found in your blood, and are responsible for fighting infection. After becoming infected, the CD4 cells are destroyed by HIV. Although the body will attempt to produce more CD4 cells, their numbers will eventually decline and the immune system will stop working. This leaves a person who is infected with HIV with a high risk of developing a serious infection, or disease, such as cancer.

What is a retrovirus?

HIV is a special type of virus known as a retrovirus. Retroviruses spread by breaking down the DNA in our cells and then reassembling it to make copies of itself. Retroviruses are challenging to treat as they can rapidly alter (mutate) into new strains of virus.

What is AIDS?

Acquired Immune Deficiency Syndrome (AIDS) is a term that is used to describe the latter stages of HIV, when the immune system has stopped working and the person develops a life-threatening condition, such as pneumonia (infection of the lungs).

The term 'AIDS' was first used by doctors when the exact nature of the HIV virus was not fully understood. However, the term is no longer widely used because it is too general to describe the many different conditions that can affect somebody with HIV. Specialists now prefer use the terms 'advanced', or 'late stage' HIV infection.