Clinical Progression of HIV
Typical course of HIV infection that shows the relationship between the levels of
HIV (viral load) and CD4+ T cell counts over the average course of untreated HIV
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, seeding 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.
Shielded from the immune system, the virus lies dormant for an extended period of
time. In the acute phase of infection, up to 70 percent of HIV-infected people suffer
The Immune System Strikes Back
Two to 4 weeks after exposure to the virus, the immune system fights back with killer
T cells (CD8+ T cells) and B-cell-produced antibodies. At this point, HIV levels
in the blood are dramatically reduced. At the same time, CD4+ T cell counts rebound,
and for some people the number rises to its original level.
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.
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.
Information published courtesy of NIAID
This article was last modified in: 06/18/2012