People with aids become sick and are unable to fight off infection explain why this occurs

H - Human - This particular virus can only infect human beings.

I - Immunodeficiency - HIV weakens your immune system by destroying important cells that fight disease and infection. A "deficient" immune system can't protect you.

V - Virus - A virus can only reproduce itself by taking over a cell in the body of its host.

HIV is a lot like other viruses, including those that cause the "flu" or the common cold. But there is an important difference - over time, your immune system can clear most viruses out of your body. That isn't the case with HIV - the human immune system can't seem to get rid of it. That means that once you have HIV, you have it for life.