CAT and viral infectious disease: During viral infections, however, the rate of intracellular ROS production exceeds the antioxidant capacity in cells, causing oxidative stress, which consequently leads to the depletion and deficiency of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), and the depletion of non-enzymatic free radical scavengers such as vitamin E (α-tocopherol), vitamin C (ascorbate), glutathione (GSH), β-carotene, and melatonin [296, 297, 299–301].