Seroconversion

Seroconversion is the point at which a person's immune system develops enough antibodies against an infection for those antibodies to be detected by a blood or oral fluid test. In HIV, it usually happens within a few weeks of infection and marks the end of the earliest "acute" phase, when the virus is multiplying quickly and the viral load is high. Because most standard HIV tests look for antibodies, a test taken before seroconversion may read negative even though the virus is present, which is why testing has a window period. Many people experience flu-like symptoms during this time, sometimes called seroconversion illness, though some have no symptoms at all. Newer antigen/antibody tests can detect HIV earlier than antibody-only tests.