It should be remembered that the most reliable serologic evidence of an ongoing infection is based on a fourfold increase in the titer of IgG (or IgG plus IgM) antibodies during the evolution of the disease episode based on two serum samples collected with an interval of 7 to 10 days or longer, and/or the appearance of IgM antibodies during the evolution of the disease. Here, CD40LG is linked to infection.