|More than 1 out of every 5 Americans with HIV may not know they're infected.|
Do you know your status? Find an HIV testing site near you at http://hivtest.cdc.gov.
The most common tests examine a blood sample for evidence that a person's body is fighting an HIV infection. These tests detect HIV antibodies, which are substances the body creates in response to being infected with HIV.
However, during the first several weeks of infection, these tests may not reveal the infection. This is because it takes some time for the immune system to produce enough antibodies for the antibody test to detect. This is a time when it is very easy for a person with the virus to pass it on to someone else (97% of people will develop detectable antibodies in the first 3 months after infection, but for a small percentage of people it can take longer). In these cases, different tests can directly look for HIV's genetic material in the blood.
National Institute of Allergy and Infectious Diseases has more information about HIV testing.
Diagnosis in Children & Youth
There are special challenges in diagnosing HIV in infants and youth.
Because the HIV antibody from HIV-infected mothers passes to their infants, finding the HIV antibody in an infant does not indicate that the infant has become HIV-infected. Maternal HIV antibody in an uninfected infant can persist as long as 12 to 18 months before it disappears. Therefore, an HIV antibody test cannot be used to diagnose HIV infection in infants under age 18 months; rather, a test that directly detects HIV's genetic material is required.
The challenge in youth is different: Young people tend to think they're not at risk for HIV. This makes them less likely to seek testing. One 1 in 5 of all Americans with HIV don't know they're infected, but almost 3 in 5 HIV-positive youth of ages 13 to 24 don't know their HIV status, according to the centers for Disease Control and Prevention.