ASMT and viral infectious disease: As to the decrease of 5-MIA, it might attribute to the reduction or inhibition of acetylserotonin O-methyltransferase, the enzyme catalyzing 5-HIAA degrading into 5-MIA and as well as the melatonin biosynthesis requires, and the suppression of melatonin has been reported to contribute to the initial cytokine storm in viral infections [23].