To investigate NS1 antibody responses in patients with acute secondary dengue infection, we recruited 76 patients with acute dengue, and through analysis of patient IgM:IgG antibody ratios determined that 55/76 patients had a secondary dengue infection (IgM:IgG antibody ratio < 1.2)23 and were included in the analyses of NS1 antibody responses. The gene discussed is CD40LG; the disease is dengue disease.