Based on IgM and IgG data, we attributed CMV DNAemia positivity detected in 81% of the patients to the reactivation of CMV latent infection (IgG positive and IgM negative, n = 102), and in 19% of the patients to the primary CMV infection (IgM positive, n = 24). The gene discussed is CD40LG; the disease is disease arising from reactivation of latent virus.