DDC and COVID-19: Our group has previously identified the impact of SARS-CoV-2 infection on the gene expression of the dopamine biosynthetic enzyme L-Dopa decarboxylase (DDC), and of other genes associated with DDC and SARS-CoV-2 infection, such as the ACE2/dACE2 locus, and the HIF-target gene EPO, in the nasopharyngeal swab samples of COVID-19 patients with mild or no symptoms.