HIV infection can be divided into following different stages:- 1. Acute Primary Infection 2. The Immune System Strikes Back 3. Clinical Latency 4. Clinical Latency.
Stage # 1. Acute Primary Infection:
Once HIV enters the body, the virus infects a large number of CD4+ T cells and replicates rapidly. During this acute phase of infection, the blood has a high number of HIV copies (viral load) that spread throughout the body, propagating in various organs, particularly the lymphoid organs such as the thymus, spleen, and lymph nodes. During this phase, the virus may integrate and hide in the cell’s genetic material. In this phase of infection, up to 70 percent of HIV-infected people suffer flu-like symptoms.
Stage # 2. The Immune System Strikes Back:
Two to 4 weeks after exposure to the virus, the immune system fights back with CD8+ T cells and antibodies. At this point, HIV levels in the blood are significantly reduced. At the same time, CD4+ T cell counts rebound, and for some people the number rises to its original level.
Stage # 3. Clinical Latency:
During this phase, a person infected with HIV may remain free of HIV- related symptoms for several years despite the fact that HIV continues to replicate in the lymphoid organs where it initially seeded.
Stage # 4. Progression to AIDS:
The immune system eventually deteriorates to the point that the human body is unable to fight off other infections. The HIV viral load in the blood dramatically increases while the number of CD4+ T cells drops to dangerously low levels. An HIV-infected person is diagnosed with AIDS when he or she has one or more opportunistic infections, such as pneumonia or tuberculosis, and has fewer than 200 CD4+ T cells per cubic millimeter of blood.