IFNB1 and Dengue hemorrhagic fever: Although not significant (p = 0.14), serum IFNβ levels were lower in the febrile phase in those who progressed to develop DHF (median 0, IQR 0 to 39.4 pg/ml), compared to those who had DF (median 37.1, IQR 0 to 65.6 pg.ml) (Fig 3A).