While some studies reported similar serum levels of IFN-α or IFN-β in DF and DHF in Thai and Mexican patients [188, 191], several other reports from Brazil, Mexico, Colombia, Taiwan, India, and Thailand showed higher levels of IFN-α in patients with milder dengue disease [77, 190, 193–196], suggesting that a robust production of IFN-α may be correlated with a better clinical condition with respect to dengue infection and disease progression. This evidence concerns the gene IFNA2 and dengue disease.