Basics of HIV

What is HIV?

Human Immunodeficiency Virus (also known as HIV) is the virus that causes HIV infection in humans. HIV weakens the immune system by attacking a special type of white blood cell called a “CD4” cell. Over time, HIV destroys so many of these cells that the body cannot fight off infections and disease. There is no cure for HIV infection, but with antiretroviral therapy (ART), HIV infection can be controlled. Based on the CD4 count (cells/ml), HIV infection is defined as Stage 1 (CD4>500), Stage 2 (CD4 200-499 cells/ml) and Stage 3 (AIDS) (<200 cells/ml). Stage 3, also known as Acquired Immunodeficiency Syndrome (AIDS), is the final and most serious stage of HIV infection. A person can have HIV without having AIDS. HIV is spread through contact with certain body fluids from a person infected with HIV:

  • Blood
  • Semen
  • Pre-seminal fluids
  • Rectal fluids
  • Vaginal fluids
  • Breast milk

The spread of HIV from person to person is called HIV transmission. In the United States, HIV is spread mainly by having sex (vaginal and/or anal) or sharing injection drug equipment, such as needles, with someone who has HIV. HIV can also pass from an HIV-infected woman to her child during pregnancy, childbirth (also called labor and delivery), or breastfeeding. This spread of HIV is called mother-to-child transmission of HIV.

In the past, some people were infected with HIV after receiving a blood transfusion or organ transplant from an HIV-infected donor. Today, this risk is very low because the supply of donated blood and organs is carefully tested in the United States. You can’t get HIV by shaking hands with, hugging, or closed-mouth kissing a person infected with HIV. You can’t get HIV from contact with objects such as toilet seats, door knobs, or dishes used by a person infected with HIV.