Test Details: Cytomegalovirus (CMV) is a member of the Herpesviridae family of viruses and usually causes asymptomatic infection after which it remains latent in patients, primarily within bone marrow derived cells. Mild symptoms include sore throat, mild fever, tiredness, swollen glands, malaise, etc. A positive CMV IgG and IgM when you have symptoms means it is likely that you have been exposed to CMV for the first time recently or a previous CMV infection has been reactivated. A positive CMV IgM and negative IgG means you may have very recently been infected. A negative CMV IgM and positive IgG means you may have past exposure.