Strikingly, 71.2% of Tfh cells in immune-modulated ZIKV infection expressed IFN-γ, the key cytokine of Th1 cells, much higher than that in uninfected control (10%), those inoculated with inactivated ZIKV (19.7%), or ZIKV only (35.8%) (Fig. 2b). Here, IFNG is linked to Zika virus infectious disease.