In dengue patients, C2 levels correlated with the levels of C4b, C5, C5a and factor D (Spearman’s rho = 0.5, 0.39, 0.61, − 0.25; P < 0.0001, < 0.0001, < 0.0001 and = 0.0002, respectively). The gene discussed is C5; the disease is dengue disease.