Question: how long does it take for monospot to be positive?
Answer: Following acute infection, the increase in IgM titers peaks after 4-8 weeks and usually remain positive for as long as 1 year. The Monospot heterophile antibodies follow the same time course as the IgM VCA titers. Rarely, cross-reactivity occurs between VCA antibodies to EBV and those to CMV or toxoplasmosis.