Chronic HIV Infection

Physical symptoms

Most people with HIV infection have no symptoms for many years. In fact, some people with HIV remain symptom-free for 10 years and longer. This is because the CD4 cells that HIV destroys continue to be replaced, enabling them to keep up the fight against the virus, sometimes for years. However, the balance of power between the immune system and HIV eventually begins to shift in favor of the virus, at which time symptoms of more advanced infection begin to appear.

The inside story

Although it may seem like nothing is happening during this period, the immune system and HIV are engaged in a grim battle. Each day, billions of CD4 cells are created and then destroyed in the battle against HIV. Eventually, the balance of power shifts in favor of the virus. When this occurs, the immune system weakens, making the body vulnerable to AIDS-defining illnesses.

Demonstration of CD4-cell turnover

The above analogy represents what happens to the CD4 cells in this stage of HIV infection. The amount of water flowing into pail A equals the amount of water flowing out of the pail through a tap; thus the water remains at a constant level. Similarly, in an individual who is not infected with HIV, CD4-cell production is equal to CD4-cell turnover; so the level of CD4 cells in the body remains relatively constant.

However, in an HIV-infected person, a large number of CD4 cells are destroyed by HIV (represented by the hole in the bottom of pail B). The total amount of water flowing out of pail B, through the tap and the hole, exceeds the quantity of water flowing into the pail, and eventually, the pail drains and becomes dry. Similarly, when the decline in CD4 cells exceeds CD4-cell production, there are no longer enough cells left to fight the virus.