WASHINGTON (AP) — The Food and Drug Administration has approved the first over-the-counter HIV test, allowing Americans to test themselves for the virus that causes AIDS in the privacy of their homes.

The OraQuick test detects the presence of HIV in saliva collected using a mouth swab. The test is designed to return a result within 20 to 40 minutes.

Government officials estimate one-fifth, or about 240,000 people, of the 1.2 million HIV carriers in the U.S. are not aware they are infected. Testing is one of the chief means of slowing new infections, which have held steady at about 50,000 per year for two decades.