The anti-oxidative effect of melatonin cooperates with its anti-inflammatory actions by up-regulating anti-oxidative enzymes (e.g. superoxide dismutase), down-regulating pro-oxidative enzymes (e.g. nitric oxide synthase), and it may also interact directly with free radicals, functioning as free radical scavenger [3,4]. Viral infections and their replication constantly generate oxidized products. In a SARS-induced ALI model, the production of oxidized low density lipoprotein activates innate immune response by the overproduction of IL-6 alveolar macrophages via Toll-like receptor 4 (TLR4)/NF-kB signaling, thereby leading to ALI [36]. TLR4 is a receptor for the innate immune system, and it is also a therapeutic target for melatonin. In brain ischemia, gastritis and periodontitis disease models, melatonin has documented anti-inflammation actions via TLR4 signaling [[37], [38], [39]]. The anti-oxidative effect of melatonin has also been confirmed in ALI caused by radiation, sepsis and ischemia-reperfusion [4,40,41]. In ALI/ARDS patients, especially when the disease is advanced and in patients treated in intense care units (ICUs), severe inflammation, hypoxemia and mechanical ventilation with high oxygen concentrations inevitably increases oxidant generation locally and systematically [42,43]. Accordingly, we speculate that excessive oxidation also is likely involved in COVID-19. The extensive studies of Gitto et al. [44,45], who used melatonin to treat newborn infants with respiratory distress, has documented the anti-oxidant and anti-inflammatory actions of melatonin in the lung. Thus, it is likely that the application of melatonin would be beneficial in controlling the inflammation and oxidation in coronavirus infected subjects.