1.The macrophages continue to produce the virus and in this way act like a HIV factiry.Simultaneously, HIV enters into helper T-lymphocytes(TH),replicates and produces progeny viruses.

2.The [progeny viruses released in the blood attack other helper T-lymphocytes.This is repeated,leading to a progressive decrease in the number of helper T-lymphocytes in the body of the infected person.

3.During this period,the person suffers frombouts of fever, diarrhoea and weight loss.Due to decrease in the number of helper T-lymphocytes, the person starts suffering from infections that could have been otherwise overcome such as those due to bacteria, such as those due to bacteria, such as mycobacterium, viruses, fungi and even parasites like Toxoplasma.

A widely used diagnostic test for AIDS is enzyme Linked Immuno Sorbent Assay (ELISA).