HIV is a virus spread through body fluids that affects specific cells of the immune system, called CD4 cells, or T cells. Over time, HIV can destroy so many of these cells that the body can't fight off infections and disease. When this happens, HIV infection leads to AIDS.
Only certain fluids—blood, semen (cum), pre-seminal fluid (pre-cum), rectal fluids, vaginal fluids, and breast milk—from an HIV-infected person can transmit HIV. These fluids must come in contact with a mucous membrane or damaged tissue or be directly injected into the bloodstream (from a needle or syringe) for transmission to possibly occur. Mucous membranes can be found inside the rectum, the vagina, the opening of the penis, and the mouth.
In the United States, HIV is spread mainly by:
Less commonly, HIV may be spread by:
Your life matters and staying healthy is important. It's important for you, the people who care about you, and your community. Knowing your HIV status gives you powerful information to help you take steps to keep you and your partners healthy. You should get tested for HIV, and encourage your partners to get tested too. If you test positive, you can get on treatment to stay healthy for many years and reduce the chance of transmitting HIV to your sex partners. To find a testing site near you, call 1-800-CDC-INFO (232-4636), visit hivtest.cdc.gov, text your ZIP code to KNOW IT (566948), or use a home testing kit.
For people who are sexually active, there are more tools available today to prevent HIV than ever before. The list below provides a number of ways that you can lower your chances of getting HIV. The more of these actions you take, the safer you can be.
The immune system usually takes 2 to 8 weeks to make antibodies against HIV (the average is 25 days). Although most HIV tests look for these antibodies, some look for the virus itself. The period after infection but before the test becomes positive is called the window period.
Deciding when to get tested therefore depends on when you may have been exposed and which test is used. You can ask your health care provider about the window period for the HIV test you are taking. If you are using a home test, you can get that information from the materials included in the packaging of the test.
A few people will have a longer window period, so if you get a negative test result in the first 3 months after possible exposure, you should get a repeat test after 3 months. Ninety-seven percent of people will develop antibodies in the first 3 months after they are infected. In very rare cases, it can take up to 6 months to develop antibodies to HIV.
Between the time you were possibly exposed and when you receive your test results:
HIV testing during each pregnancy is important because, if your result is positive, treatment can improve your health and greatly lower the chance that you will pass HIV to your infant before, during, or after birth. The treatment is most effective for preventing HIV transmission to babies when started as early as possible during pregnancy. However, there are still great health benefits to beginning preventive treatment even during labor or shortly after the baby is born.
CDC recommends that health care providers screen all pregnant women for HIV, talk to them about HIV or give them written materials, and, for women with risk factors, provide referrals to prevention counseling. Screening all pregnant women for HIV, and giving them the right medical care, helped decrease the number of babies born with HIV from a high of 1,650 in 1991 to 127 in 2011.
For heterosexual couples where one partner has HIV and the other does not, PrEP is one of several options to protect the uninfected partner during conception and pregnancy.
The most common HIV test is the antibody screening test (immunoassay), which tests for the antibodies that your body makes against HIV. The immunoassay may be conducted in a lab or as a rapid test at the testing site. It may be performed on blood or oral fluid (not saliva).
Because the level of antibody in oral fluid is lower than it is in blood, blood tests tend to find infection sooner after exposure than do oral fluid tests. In addition, most blood-based lab tests find infection sooner after exposure than rapid HIV tests. Newer immunoassay tests can find HIV as soon as 3 weeks after exposure to the virus. Several lab tests now in use can detect both antibodies and antigen (part of the virus itself), so find recent infection earlier than tests that detect only antibodies.
The rapid test is an immunoassay used for screening, and it produces quick results, in 20 minutes or less. Rapid tests use blood or oral fluid to look for antibodies to HIV. If an immunoassay (lab test or rapid test) is conducted during the window period (i.e., the period after exposure but before the test can find antibodies), the test may not find antibodies and may give a false-negative result. All immunoassays that are positive need a follow-up test to confirm the result.
Follow-up diagnostic testing is performed if the first immunoassay result is positive. Follow-up tests include: an antibody differentiation test, which distinguishes HIV-1 from HIV-2; an HIV-1 nucleic acid test, which looks for virus directly; or the Western blot or indirect immunofluorescence assay, which detect antibodies.
Immunoassays are generally very accurate, but follow-up testing allows you and your health care provider to be sure the diagnosis is right. If your first test is a rapid test, and it is positive, you will be directed to a medical setting to get follow-up testing. If your first test is a lab test, and it is positive, the lab will conduct follow-up testing, usually on the same blood specimen as the first test.
False-positive tests are rare. If tests are conducted during the window period, they can give a false-negative result.
Currently there are only two home HIV tests: OraQuick In-home HIV test and the Home Access HIV-1 Test System. If you buy your home test online, make sure the HIV test is FDA-approved.
The OraQuick In-Home HIV Test provides rapid results in the home. The testing procedure involves swabbing your mouth for an oral fluid sample and using a kit to test it. Results are available in 20 minutes. If you test positive, you will need a follow-up test. The manufacturer provides confidential counseling and referral to follow-up testing sites. Because the level of antibody in oral fluid is lower than it is in blood, oral fluid tests find infection later after exposure than do blood tests. Up to 1 in 12 people may test false-negative with these tests.
The Home HIV Access HIV-1 Test System is a home collection kit, which involves pricking your finger to collect a blood sample, sending the sample to a licensed laboratory, then calling in for results a few days later. If the test is positive, a follow-up test is performed right away. This test is anonymous. The manufacturer provides confidential counseling and referral to treatment. The tests conducted on the sample collected at home find infection later than most lab-based tests offered by providers.
RNA tests detect the virus directly (instead of the antibodies to HIV) and thus can detect HIV at about 10 days after infection—as soon as it appears in the bloodstream, before antibodies develop. These tests cost more than antibody tests and are generally not used as a screening test, although your doctor may order one as a follow-up test, after a positive antibody test, or as part of a clinical workup.
Getting tested for HIV is an important step in taking charge of your life. More and more black women are standing up and getting tested for HIV. They are looking out for themselves and doing what they need to do to stay healthy. Regardless of the results, there are treatment and support programs available to help you live a healthy and productive life. To find an HIV testing location near you, use the Take Charge. Take the Test.™ site locator or call 800-CDC-INFO (800-232-4636).
If you receive a negative HIV test result within the “window period”, you need to have a follow-up test to confirm your results. See When should I get tested for HIV? for more information. You can also confirm when you need to be retested with a health professional.
If you receive a negative test after the window period, remember there are things you can do to stay negative. See How can I protect myself from HIV? for ways to prevent HIV infection.
If you had a rapid screening test, the testing site will arrange a follow-up test to make sure the screening test result was correct. If your blood was tested in a lab, the lab will conduct a follow-up test on the same sample. If the follow-up test is also positive, it means you are HIV-positive.
The sooner you take steps to protect your health, the better. Early treatment with antiretroviral drugs and a healthy lifestyle can help you stay well. Prompt medical care prevents the onset of AIDS and some life-threatening conditions.
Here are some important steps you can take right away to protect your health:
To avoid giving HIV to anyone else: