Sepsis is caused by a combination of factors related to the particular invading pathogen(s) and to the status of the immune system of the host.  The early phase of sepsis characterized by excessive inflammation (sometimes resulting in a cytokine storm ) may be followed by a prolonged period of decreased functioning of the immune system .  Either of these phases may prove fatal. On the other hand, systemic inflammatory response syndrome (SIRS) occurs in people without the presence of infection, for example, in those with burns , polytrauma , or the initial state in pancreatitis and chemical pneumonitis . However, sepsis also causes similar response to SIRS.