Before the causative agents was not yet known, patients presenting with symptoms of severe immunosuppression was called AIDS (Acquired Immune Deficiency Syndrome). Their clinical presentation varied, but shared enough features to justify their being treated as part of a syndromic disease caused by a single pathogen (HIV).
The natural course of HIV disease varies between infected individual. Some may remain healthy approximately 10-15 years after seroconversion, whereas others may progress to symptomatic disease within a few years on infection.
When first identified, the new syndrome lacked an agreed-upon, accurate definition, and its causative agent was unknown. Therefore, the U.S Centers for Disease Control and Prevention (CDC) suggested that a combination of opportunistic infection and immunosuppression were indicative of AIDS.
Once the causative agent, HIV, was identified, the definition was revised appropriately. The CDC and the World Health Organization (WHO) developed simplified diagnostic criteria that considerably eased the difficulties.
AIDS is a clinical syndrome of diseases that results from the profound immunosuppression that permits opportunistic infections to replicate in an uncontrolled manner. WHO/Bangui AIDS case definition consist of major signs and minor signs.
Major signs are unexplained weight loss more than 10% of body weight, unexplained chronic diarrhea more than one month duration, and prolonged fever more than one month duration. Minor signs are persistent cough more than one month, pruritic HIV rashes, recurrent herpes zoster, oropharyngeal candidiasis, chronic progressive herpes simplex, and generalized lymphadenopathy. Any two major signs or one major plus two minor signs, constitute an AIDS diagnosis.