Interestingly, although it has been shown in previous studies that the concentrations of MMPs are increased in dengue patients [13, 32] and MMP-9 upregulation is positively correlated with the disease severity and vascular leakage of dengue [31, 32, 42, 43], we observed a significant increase in the serum level of MMP-9 only in dengue patients with warning signs, not in severe dengue patients. The gene discussed is MMP9; the disease is dengue disease.