The human immunodeficiency virus (HIV) is the virus that causes AIDS (acquired immunodeficiency syndrome). The virus gets its name because it infects and damages part of the immune system — the body's natural defense system.

Often the only way to know if someone is infected with HIV is through testing. That's because people who are HIV positive may not know that they have the virus. Most of the signs that someone has HIV don't show up until that person has developed full-blown AIDS. By that point, the person is sicker and the disease can be harder to treat, and they may have spread it to others without knowing.

Here are the facts on what's involved in getting tested — and who should get tested for HIV and why.

Who Is at Risk?

The only known way for HIV to be transmitted from one person to another is when it is spread through the fluids from an infected person's body. Thousands of U.S. teens become infected with HIV each year.

When teens in the United States become infected with HIV, it usually happens in one of two ways:

1. By sharing needles used to inject drugs or other substances (including needles used for injecting steroids, tattooing, piercing, and body art). If the person who has used the needle is infected with HIV, his or her blood on the needle can infect anyone else who uses the same needle.
2. Through unprotected sex including anal, vaginal, and oral sex. This can happen when body fluids such as semen (cum), vaginal fluids, or blood from an infected person get into the body of someone who is not infected. Everyone who has unprotected sex with an infected person is at risk of contracting HIV, but people who already have another sexually transmitted disease (STD) are even more at risk.

Children can be infected with HIV if an infected pregnant woman passes the virus to her unborn child. Treating the mother and child around the time the baby is delivered, delivering by cesarean section, and avoiding breastfeeding can reduce the baby's risk of infection.

Reasons to Get Tested for HIV

If you have had unprotected sex (sex without a condom) or have shared needles with someone else, you should be tested for HIV. If you’ve had sex with a condom, you also should be tested since condoms are effective when used correctly, but are not perfect.

Early detection is key in fighting HIV and AIDS because:

• There is no cure for HIV, so early detection allows a person to get medical treatment that can slow the advancement and effects of the disease.
• Someone who learns he or she is infected can take the proper steps and precautions to prevent spreading the disease.
• Couples who want to get pregnant can take action to try to prevent their baby from being born with HIV.

Another reason to get tested is peace of mind: A negative test result can be a big relief for someone who is worried that he or she might be infected.

What the Tests Do

Most HIV tests don't actually look for the virus itself; they look for the antibodies that indicate HIV is present in the body.

When someone has HIV, the body's immune system makes antibodies to fight the virus. Unlike the antibodies our immune systems make that successfully fight off other infections, the antibodies to HIV cannot stop the virus. But their presence in great numbers is what appears in test results. The antibodies can take anywhere from 2 weeks to 6 months to appear in detectable quantities. So when someone has an HIV test, it may not show an infection that could have occurred in the last 6 months.

Types of HIV Tests

• EIA or ELISA Tests. These are the most common type of HIV test. It generally takes a few days to 2 weeks to get the results. This screening tests the blood sample for HIV antibodies. If the screening results come back positive, showing the presence of HIV antibodies, a Western blot is done.
• Western Blot. If the EIA or ELISA test is positive, the results are confirmed by another test called a Western blot. If both of these tests are positive, the person is almost certainly infected with the HIV virus. In rare cases, the EIA test can produce false positives when antibodies other than the HIV antibodies respond to the tests. In these cases, the Western blot will be negative.
• Rapid Tests. Rapid tests are the speedy alternative to the EIA and ELISA tests — and they're just as accurate. While a standard blood test can take 1-2 weeks to return results, a rapid test is ready in about 20 minutes. Rapid tests are not available in a lot of places. Just like with the EIA and ELISA tests, the rapid tests need to be confirmed with the Western blot test as well.
• At-Home Tests. Many at-home testing kits are available over the counter or online, but only one of them, the Home Access kit, is approved by the U.S. Food and Drug Administration (FDA). The Home Access test is available at most local drugstores and works in much the same way a home diabetes test works. The user pricks his or her finger and puts the blood on a specially prepared card. The card is then sent into a laboratory, where it is analyzed and the results are available (by phone with an anonymous identification number) in about 7 days. There is also a Home Access Express kit, which can provide anonymous results by the next business day. The Express kit is slightly more expensive than the 7-day kit. The Home Access test has been found to be more than 99.9% accurate.
• Other tests that allow a person to read the results at home without sending in a sample are considered to be inaccurate and should not be used.

Where to Get Tested

People can get tested for HIV at a variety of different places, such as doctors' offices, health departments, hospitals, and sites that specialize in HIV testing. Some places, like certain clinics or hospitals, offer tests at little or no cost.

Anonymous Test Sites. An anonymous test site will never ask for a person's name or other identifying details. Instead, anyone being tested goes by a number and he or she is the only one who knows the results of the test. Although people go by numbers at anonymous sites, they aren't treated like just another number. Many anonymous sites have counselors available to talk with the person being tested, both before and after testing. No written record of the test result is kept at anonymous test sites.

Confidential Test Sites. Confidential testing means that at a certain point in the process the person being tested will need to identify themselves. The results may appear as a written report in his or her medical file.

Every state has different laws pertaining to HIV testing, so it's always a good idea to check to see what is available in a particular area.

If Test Results Are Positive

Someone who tests positive for HIV should:

• Contact a doctor immediately to discuss ways to slow the progress of the infection. Often a doctor will do more tests to evaluate the status of the virus. A person with a positive test may want to talk to a doctor who is an HIV specialist.
• Stop any activity that has an adverse affect on the body's immune system. These include excessive drinking, drug use, unhealthy eating, and smoking.
• Have additional tests to look for the presence of other STDs and diseases. When HIV was passed on, other STDs may have been passed on as well. Because HIV weakens the immune system, an HIV-positive person's body may need more help fighting off other diseases.
• Let past, current, and future sexual partners know about the infection. People who may have been exposed should be tested so that they can be treated as well. Condoms should always be used for future sexual encounters in order to help avoid infecting others.

People who discover they are HIV positive may feel frightened, isolated, afraid to talk to friends and family, or worried that they will be discriminated against or misunderstood. Talking to a counselor or other mental health professional can help them deal with these and other feelings.

Some health clinics that specialize in HIV and AIDS offer counseling services or know of support groups for those living with HIV. These safe environments offer a chance to discuss any fears and get answers to questions from people who care and understand what someone with HIV is going through.

There is no cure for HIV, but having the virus is not the death sentence it once was. Governments and scientists are putting a lot of money and research into treating — and, hopefully, eventually curing or immunizing people against — HIV. With treatments improving rapidly, people who find out they have the disease today can look forward to living a normal life for many years to come.

Reviewed by: Larissa Hirsch, MD
Date reviewed: September 2010