IFIH1 and hand, foot and mouth disease: Simple linear regression analysis were performed to show the variance in DDX58 expression accounted by HFMD severity (R square = 0.293, p<0.001), by DDX58 methylation (R square = 0.058, p = 0.008), and the variance in IFIH1 expression accounted by HFMD severity (R square = 0.033, p = 0.046), by IFIH1 methylation (R square = 0.007, p = 0.347).