HIV (human immunodeficiency virus) is a virus that attacks the body"s immune system. The virus is spread through a specific type of body fluid called CD4 cells, also known as T-cells. These special cells help the immune system fight off infections. Untreated, HIV reduces the number of CD4 cells (T-cells) in the body. Over time, HIV can destroy so many of these cells that the body can no longer fight off infections and disease. In addition, this damage to the immune system makes it very difficult for the body to fight off infections and other diseases. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome), which also makes it easier for infections or cancers to take advantage of a very weak immune system."