IL1RL1 and COVID-19: Clinical trials have shown significantly elevated levels of serum cytokines, including IL-33 and ST2, in 100 COVID-19 subjects, and elevated levels of IL-33 and its specific receptor ST2 were identified as an independent predictor of poor prognosis for SARS-CoV-2 patients aged < 70 years, indicating that IL-33 is very likely to be involved in the pathological process of COVID-19.