The seropositivity rates (anti-CHIKV IgM and/or anti-CHIKV IgG Ab positive rate) against CHIKV were 32/196 (16.3%) for dengue-suspected pediatric patients, 360/691 (52.1%) for blood donors, and 184/237 (77.6%) for healthy volunteers. Here, CD40LG is linked to dengue disease.