EBV antibodies (Epstein-Barr virus serology)

Epstein-Barr virus (EBV) is an extremely common herpesvirus and the usual cause of infectious mononucleosis ('mono' or glandular fever). EBV serology is not a single test but a small panel of antibodies, and it is the pattern across them that matters. The key building blocks are IgM and IgG antibodies to the viral capsid antigen (VCA), and an antibody to the Epstein-Barr nuclear antigen (EBNA). In a current, acute infection, VCA IgM appears early and EBNA is still absent. As the infection resolves over weeks to months, VCA IgM fades, VCA IgG persists for life, and EBNA IgG appears and also persists — so the combination of VCA IgG plus EBNA, without VCA IgM, signals past infection and lifelong immunity. Because the great majority of adults were infected in childhood or adolescence (often without a clear illness), a positive past-exposure result is the norm rather than a finding of concern. The serology is used mainly to confirm mononucleosis when the rapid 'monospot' test is negative or unclear, or to establish whether someone has been exposed before.

• VCA IgM positive (with EBNA negative) — a current or recent acute infection, consistent with infectious mononucleosis.
• VCA IgG and EBNA positive (IgM negative) — past infection and lifelong immunity; very common in adults.
• A rising or evolving pattern — helps time and confirm an acute infection.
• EBV in a person with weakened immunity — reactivation can matter and is interpreted carefully.

• All antibodies negative — no evidence of past or current EBV infection; the person is susceptible.
• A negative result early in illness — antibodies can take days to appear, so timing matters.