- People with human immunodeficiency virus (HIV) can sometimes develop thinking and memory problems. These problems can vary widely, from few symptoms to severe problems with memory and concentration. It initially was thought that good HIV treatment could prevent almost all HIV-related memory problems. However, even people with low HIV viral loads can have these problems. It may be caused by HIV affecting the brain and spinal fluid. It is not yet clear why HIV causes these problems and why they may be worse in some people than others. Researchers want to study people with HIV and healthy volunteers to see how HIV may affect people with only small amounts of the virus in their blood.