Evidence for prior exposure to HBV (antibodies to HBc) was found in 344 (50%) of 694 patients tested, and evidence for chronic HBV infection (antibodies to HBc with positive results for hepatitis B surface antigen and negative results for IgM to HBc) was detected in 69 (11%) of 618 dengue patients and 9 (19%) of 47 OFI patients. Here, CD40LG is linked to dengue disease.