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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).
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.
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 OIs.
You do not have AIDS as soon as you are infected with HIV. You can live with HIV (be HIV+) for many years with no signs of disease, or only mild-to-moderate symptoms. But without treatment, HIV will eventually wear down the immune system in most people to the point that they have low numbers of CD4 cells and develop OIs.
The US Centers for Disease Control and Prevention (CDC) identifies someone as having AIDS if she or he is HIV positive and has one or both of these conditions:
People with AIDS can rebuild their immune system with the help of HIV drugs just like people with HIV who do not have AIDS. Even if your CD4 cell count goes back above 200 or an OI is successfully treated, you will still have a diagnosis of AIDS. This does not necessarily mean you are sick or will get sick in the future. It is just the way the public health system counts the number of people who have had advanced HIV disease.
Most people cannot tell that they have been exposed or infected. Symptoms of HIV infection may show up within two to four weeks of exposure to HIV, and can include a fever, swollen glands, muscle aches, headache, or rash. Some people do not notice the symptoms because they are mild, or people think they have a cold or the flu. The only way to know for sure if you are infected is to take an HIV test.
The CDC estimates that about one in five HIV+ people in the US do not know they have HIV. Many of these people look and feel healthy and do not think they are at risk. But the truth is that anyone of any age, gender, race, sexual orientation, social group, or economic class can become infected. For more on how HIV is spread, see our info sheet on HIV transmission.
Answer the following questions:
If you answered yes to any of these questions, you should definitely get an HIV test. In the US, it is now recommended that everyone age 13-64 be screened for HIV at least once.
If you are worried because you think you may have been exposed to HIV, get tested. Then, if you learn that you are negative (not infected), you can stop worrying. If you test HIV+ there are effective medications to help you stay well. But you cannot get the health care and treatment you need if you do not know your HIV status (whether you are HIV+ or HIV-negative). Being unaware of your status also means that you could pass HIV to others without knowing it.
For women who plan to become pregnant, testing is especially important. If a woman is infected with HIV, medical care and certain drugs given during pregnancy can lower the chance of passing HIV to her baby. For more information, see our Pregnancy and HIV info sheet.
If you have been infected, your immune system will make antibodies against HIV. Antibodies are special proteins that our bodies make to identify "intruders" like viruses and bacteria. The most common HIV tests look for these antibodies in your blood, urine, or oral fluid (not your saliva). Your body will produce antibodies to HIV after three to six months. The period between infection and your body's production of HIV antibodies is called the "window period." Having a negative HIV test after the window period means you are not infected with HIV.
If you want to get tested before the window period has passed, there are viral tests that look for the presence of HIV's genetic material in the blood and can identify an HIV infection within two to three weeks of exposure. For more information, see our HIV Testing info sheet.
There are many different types of places for you to get an HIV test. These include health clinics, private health care providers offices, HIV testing centers, and health departments. There are also HIV tests you can order online or buy over-the-counter at stores that have pharmacies (e.g., CVS, Walgreens, Walmart). These tests are ones that allow you to collect a sample or complete a full rapid test (20 minutes) in the privacy of your home.
In the US, you can go to the National HIV and STD Testing Resources website or the AIDS.gov website to find a testing site near you. You can also call the CDC's information line at 800-232-4636 or call your state's HIV/AIDS hotline (numbers listed here). To find services across the world, visit AIDSmap's e-atlas.
There is currently neither a vaccine nor a cure for HIV. The best way to prevent HIV is to use sterile needles and practice safer sex. For more information, see our info sheet on AIDS Vaccines.
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