The patient who was negative for dengue NS1 Ag was tested for the presence of this antigen on day 10 of the illness The detection of dengue IgM in CSF has been shown to have a high specificity (97%) for the diagnosis of neurologic dengue and might be associated with the neurovirulence of DENV and its ability to cause encephalitis [41]. This evidence concerns the gene CD40LG and dengue disease.