Because people with AIDS have weakened immune systems, they're more prone to infections, called opportunistic infections. Opportunistic infections are caused by organisms that typically don't cause disease in healthy people but affect people with damaged immune systems. These organisms attack when there's an opportunity to infect.
Deterioration of the immune system is caused by the decline in CD4+ T cells, which are key infection fighters. As soon as HIV enters the body, it begins to destroy these cells.
Opportunistic Infections: Brain
Cryptoccoccal Menigitis — This is a yeast-like fungus infection that usually involves the brain and lungs, although it can affect almost any organ. The fungus that causes this condition is found in soil throughout the world. It is most common in soil contaminated by bird droppings. This disease most often occurs when a person's CD4+ T cell count falls below 100 cells per cubic millimeter of blood.
