H-I-V stands for Human Immunodeficiency Virus

H-Human- This virus infects humans

I-Immunodeficiency- This virus attacks a person's immune system, causing it to become deficient and not work properly.

V-Virus- A virus is a type of germ. Viruses need living cells to grow and reproduce

HIV is a virus, a type of germ too small to see even with a powerful microscope. After a person is infected with HIV, that person becomes "HIV positive". This means that a blood test for HIV will show that the person is infected.

Some viruses, like the ones that cause colds or flu, stay in the body for only a few days. HIV, however, never goes away. Once a person is HIV positive, that person stays HIV positive. Over time, HIV infects and kills off immune cells, leaving the body unable to fight off certain kinds of infections and cancers.

A-I-D-S stands for Acquired Immuno-deficiency Syndrome

A-Acquired- This is a condition that is acquired, meaning that a person becomes infected

I-Immuno- This condition affects a person's immune system, the part of the body in charge of fighting off germs such as bacteria or virus

D-Deficiency- The immune system is weakened and does not work properly.

S-Syndrome- A person with AIDS may experience many other diseases and infections due to their weakened immune system.

AIDS is a condition that is caused by HIV. It is the name that is given to the state of weakened immunity that occurs over time when HIV is not or cannot be adequately treated. The names can be confusing, since the terms HIV and AIDS are both used to describe the same disease. HIV causes AIDS, but it can take time for AIDS to develop (usually between 2 to 10 years or longer), so a person can have HIV and not have AIDS. The term "HIV disease" can be used to describe any part of the illness, whether or not someone has developed AIDS.

An HIV-positive person is said to have AIDS when his or her immune system is so weakened by HIV that the person becomes sick with one of several opportunistic diseases or cancers including: tuberculosis, toxoplasmosis, PCP (a type of pneumonia), wasting syndrome (involuntary weight loss), candidiasis, and HIV dementia (memory impairment).

HIV infects several kinds of cells in the body. The most important cell it infects is a type of white blood cell called the CD4 lymphocyte, or CD4 T cell. White blood cells are a major part of the immune system and help fight off viruses and bacteria. A healthy person usually has a CD4 count between 600-1200. When the CD4 count drops below 200 due to advanced HIV infection, a person's immune system is weakened. They are then diagnosed with AIDS, even if they have not become sick from other infections.