IL-33 and ST2 are widely expressed throughout the human body, and low plasma or serum levels of IL-33 or high levels of sST2 are seen in numerous diseases, including cardiovascular diseases, particularly heart failure [17, 18] and stroke [19, 20], and infectious diseases, including sepsis [21, 22] and recently COVID-19 [23, 24]. Here, IL33 is linked to COVID-19.