During this time, HIV is continually replicating itself and attacking CD4 cells, but the body continues to produce more CD4 cells to replace the damaged ones. At some point, something causes HIV to gain the upper hand - possibly the body's ability to produce and replace destroyed CD4 cells slows down. The CD4 count will probably start to decline, although not always immediately. Without replacement CD4 cells, the immune system cannot function properly, and the body becomes more vulnerable to infections and conditions known as opportunistic infections. Opportunistic Infections Opportunistic infections are infections that take advantage of HIV - related damage to the immune system.
Many opportunistic infections are now treatable.
HIV can also sometimes directly attack the nervous system and can affect limbs and the brain. In some people it appears to prolong life and decrease the amount of opportunistic infections developing. For others, however, the side-effects are so extreme that they can not take the drug, as it would be detrimental to their health to do so. There has been much debate about whether people with asymptomatic HIV should take AZT, and the Concorde trial suggested that there was no overall benefit to people taking AZT at this stage. It appears so far that this is more effective than AZT alone.