systemic inflammatory response syndrome systemic inflammatory response syndrome systemic inflammatory response syndrome (sirs) is an inflammatory state affecting the whole body. it is the body's response to an infectious or noninfectious insult. although the definition of sirs refers to it as an "inflammatory" response, it actually has pro- and anti-inflammatory components. this article is about systemic inflammatory response syndrome. for the novel illnesses similar to the kawasaki disease that has been observed in children possibly linked with covid-19, see paediatric multisystem inflammatory syndrome.