According to findings, the sooner that individuals diagnosed with HIV begin treatment with antiretrovirals (ARVs), the better off they’ll be.

This is because ARVs lower the level of virus in the blood—called viral load—which reduces the risk of developing illnesses related to HIV and the chances of transmitting the virus to others. But because no test can detect the virus immediately after transmission, the Centers for Disease Control and Prevention (CDC) recommends that everyone between ages 13 and 64 get tested for HIV at least once as part of routine health care.

How soon a test can pinpoint infection depends upon different factors, including the type of exam used. If the test is one ordered by a doctor, a laboratory will check for antigens or antibodies. If these substances are found, the lab usually confirms the result with a follow-up exam on the same blood sample used for the first test.

However, if someone undergoes a rapid test for HIV that’s determined to be positive, he or she is referred to a health care provider for a follow-up screening.

Three types of diagnostic tests are employed to find HIV: exams that detect both antigens and antibodies activated by the immune system if the virus strikes; one that checks only for antibodies that the body produces against HIV; and expensive nucleic acid tests (NATs) that check for HIV in the blood. (NATs are usually used only if someone experiences high-risk exposure to the virus or early symptoms.)

The CDC stresses that testing helps folks who are HIV negative make better decisions about sex, drug use and health care, which can protect them from the virus and stop the spread of HIV.