HIV affects the ability of your body's immune system to fight off infection. If the HIV is left untreated, it will destroy a type of white blood cell called CD4 T-cells, which play an important role in your immune system. 

The number of CD4 blood cells that you have is called your CD4 count. The lower your CD4 count is, the more likely you are to show signs of illness. However, a low CD4 count is not an illness in itself. Some people remain well when their CD4 counts get lower, at least for a while. Other people with HIV may start developing symptoms before their CD4 count is lowered.

What to look out for

Common symptoms of HIV infection, especially as your CD4 counts get lower, include:

• unintentional weight loss
• chronic diarrhoea
• skin rashes, especially on your face, genitals or anus
• an increase in herpes ulcers or thrush infections in your mouth and genitals
• sweats, especially at night
• unusual tiredness
• nausea or loss of appetite
• swollen lymph glands in the neck, groin or armpits.

These symptoms can all be caused by conditions other than HIV, and do not mean you have AIDS. However, if you experience all or some of these symptoms persistently, it might be a good idea to get an HIV test, especially if you think you may have been at risk of HIV infection.

When people first become infected with HIV most of them exhibit some mild symtpoms that could be mistaken for something else.