It is generally accepted throughout the scientific community that infection with HIV is the necessary pre-condition for the development of AIDS.

It is evidently possible for an individual's immune system to be compromised in other ways, and in rare cases this can lead to the same kinds of infection as those seen in AIDS. This has been termed idiopathic CD4 lymphocytopenia or ICL. The immune suppression seen in ICL is not always the same as in AIDS however, often clearing up without treatment.

Opportunistic infections can also occur in patients whose immune systems have been suppressed by medical interventions, such as transplant patients and ones receiving cancer chemotherapy.

Although it is clear that HIV has a central role in the development of AIDS, other factors play an important role in the development of immune damage.

Some other diseases such as other sexually transmitted infections or malaria may play an additional role both in accelerating the course of AIDS and in making individuals more vulnerable to infection in the first place.

A person’s general state of health is important; fatigue, poor nutrition and recreational drug use are among many other factors that may suppress the immune system. Some studies have found that people in certain developing countries develop AIDS faster, possibly for these reasons.

Lastly, so-called ‘host factors’ are very important. The individual’s genetic makeup may make them more or less vulnerable to the damage caused by HIV.

See the HIV & AIDS Treatments Directory for a full discussion of these issues.