Test Details: The Epstein-Barr virus (EBV) is a member of the herpes virus family. It causes an illness called infectious mononucleosis, or mono. This particular test aids in the diagnosis of EBV infections (infectious mononucleosis). The Viral capsid antigen (VCA) IgG antibodies emerges during acute infection with the highest level at 2 to 4 weeks, then drops slightly, stabilizes, and is present for life. If someone is positive for VCA-IgG tests, then it is highly likely that the person has a current or recent EBV infection.