What Is HIV?
HIV stands for Human Immunodeficiency Virus. HIV is the virus that causes AIDS.
Your immune system is your body's defense system. While many viruses can be controlled by the immune system, HIV targets and infects the same immune system cells that are supposed to protect us from germs and illnesses. These cells are a type of white blood cell called CD4 cells (sometimes called T-cells).
Without medication to control the virus, in most cases, HIV takes over CD4 cells and turns them into factories that produce thousands of copies of the virus. As the virus makes copies, it damages or kills the CD4 cells, weakening the immune system. This is how HIV causes AIDS.
What Is AIDS?
AIDS stands for Acquired Immune Deficiency Syndrome. AIDS is the most advanced stage of HIV infection.
HIV causes AIDS by attacking CD4 cells, which the immune system uses to protect the body from disease. When the immune system loses too many CD4 cells, you are less able to fight off infection and can develop serious, often deadly, infections. These are called opportunistic infections (OIs).
When someone dies of AIDS, it is usually OIs or other long-term effects of HIV that cause death. AIDS refers to the weakened state of the body’s immune system that can no longer stop opportunistic infections.
Where did HIV come from?
Scientists identified a type of chimpanzee in Central Africa as the source of HIV infection in humans. They believe that the chimpanzee version of the immunodeficiency virus (called simian immunodeficiency virus, or SIV) most likely was transmitted to humans and mutated into HIV when humans hunted these chimpanzees for meat and came into contact with their infected blood. Studies show that HIV may have jumped from apes to humans as far back as the late 1800s. Over decades, the virus slowly spread across Africa and later into other parts of the world. We know that the virus has existed in the United States since at least the mid- to late 1970s.
How Do I Know If I Have HIV?
Most people cannot tell that they have been exposed or infected. Initial, or acute symptoms of HIV infection may show up within two to four weeks of exposure to HIV, and can include:
- Fever
- Swollen glands
- Sore throat
- Night sweats
- Muscle aches
- Headache
- Extreme tiredness
- Rash
Some people do not notice the symptoms because they are mild, or people think they have a cold or the flu. After the 'flu-like' symptoms that often accompany initial infection, people living with HIV can go years without showing any symptoms. The only way to know for sure if you are infected is to take an HIV test.
If you have some of the initial or acute symptoms of HIV, it is important that you be tested for HIV antigen (not just HIV antibody). Antigens are pieces of the HIV virus or viral particles. If an HIV antigen is your blood, there are tests that can identify HIV infection as quickly as two weeks after exposure to HIV.
Antibodies are proteins that your body makes to mark HIV for destruction by your immune system. The body takes one to three months and occasionally up to six months to develop antibodies to HIV. This three to six month period between getting HIV and the production of antibodies is called the "window period." Therefore, the results of tests that detect antibodies are only reliable one to three months after your exposure to HIV.
How Is HIV Spread?
HIV is spread primarily through contact with the following body fluids:
- Blood (including menstrual blood)
- Semen (“cum”) and other male sexual fluids ("pre-cum")
- Vaginal fluids
- Breast milk
The most common ways HIV is spread from person-to-person is through unprotected sex (no condoms or other barriers), sharing needles used for injecting drugs, and mother-to-child (during pregnancy, birth, or breast-feeding).
HIV is NOT spread through contact with these body fluids:
- Sweat
- Tears
- Saliva (spit)
- Feces (poop)
- Urine (pee)
In other words, you CANNOT get HIV by touching or hugging someone who is living with HIV, kissing someone living with HIV, or by using a toilet also used by someone living with HIV.
Is There a Vaccine or Cure for HIV?
There is neither a vaccine nor a cure for HIV. The best way to prevent HIV is to use consistent prevention methods, including safer sex (choosing low- or no-risk activities, using condoms, taking PrEP) and using sterile needles (for drugs, hormones or tattoos). For more information, see our fact sheet on HIV Vaccines.
