The detection of IgM antibodies against cytomegalovirus (another member of Herpesviridae that also causes neonatal infection) do not indicate primary infection, however, the IgG avidity test (force measurement of antigen-antibody interaction) can discriminate between early and late infections, and the low avidity is produced during the first month after infection and the high avidity, later [12]. Here, CD40LG is linked to infection.