IL31 and COVID-19: Compared with those in healthy volunteers, the concentrations of interleukin (IL)-6 (median 27.6 pmol/L), IL-8 (1045.1 pmol/L), IL-17A (0.8 pmol/L), IL-25 (1.5 pmol/L), and IL-31 (42.3 pmol/L) were significantly greater in the ELF of COVID-19 patients than in that of volunteers.