CD40LG and viral infectious disease: However, the data from IgG tests are useful in a) corroborating results of the IgM tests, b) providing evidence of a previous arboviral infection when IgM is not detectable, c) indicating an anamnestic response, especially in secondary DEN viral infections, and d) pointing the diagnosis toward an unsuspected arboviral infection due to the presence of intra-genus cross-reactive IgG antibodies.