What is "cytokine storm"

n. (context pathology English) An immune system - cytokine positive feedback reaction to certain infections. Suspected as being implicated in the high mortality rates of the Spanish flu outbreak of 1918-1920.

A cytokine storm, also known as cytokine cascade and hypercytokinemia, is a potentially fatal immune reaction consisting of a positive feedback loop between cytokines and white blood cells, with highly elevated levels of various cytokines.