HIV or human immunodeficiency virus infection passes through a series of stages or steps before it becomes full blown AIDS. These stages of infection as outlined in 1993 by the Centers for Disease Control and Prevention (CDC) are:
This occurs in 1 to 6 weeks after acquiring the infection. There may be symptoms in 20 to 60% patients. Common symptoms are:
Acute infection may be asymptomatic. The feeling is similar to a bout of flu.
After seroconversion, virus levels are low and replication continues slowly. CD4 and CD8 lymphocyte levels are normal. This stage has no symptoms and may persist for years together.
This stage has typical lymph node swelling of over 1cm in diameter in at least two sites apart from the groin. The lymph nodes are swollen for three months or longer and not due to any other cause.
This stage manifests with symptoms such as fever, night sweats, diarrhoea, and weight loss.
In addition, there may be infections with organisms that normally cause minor or mild illnesses. These are called opportunistic infections. This includes fungal infections like oral candidial infection, vaginal or penile candida infections, oral hairy leukoplakia, seborrhoeic dermatitis tinea infections and viral infections like herpes zoster, recurrent herpes simplex.
This collection of symptoms and signs is referred to as the AIDS-related complex (ARC) and is regarded as a prodrome or precursor to AIDS.
This stage is characterized by severe immunodeficiency. There are signs of life-threatening infections and unusual tumours. There are symptoms such as:
Other infections like tuberculosis and pneumonia may occur at this stage. This stage is characterized by CD4 T-cell count below 200 cells/mm3.
There is a small group of patients who develop AIDS very slowly, or never at all. These patients are called nonprogressors, and many seem to have a genetic difference that prevents the virus from significantly damaging their immune system.