In this study, we have quantified for the first time the plasma levels of IL-33 and sST2 in HFRS patients, analyzed the relationships between IL-33, sST2, and disease severity-indicating parameters in vivo, and explored the role of IL-33/ST2 in regulating immune response in vitro during HTNV infection. This evidence concerns the gene IL33 and hemorrhagic fever with renal syndrome.