Mild hyperthermia in the first 24 hours following injury is almost always the result of pyrogen release. The three endogenous pyrogens that mediate fever are interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α, cachetin), and interferon-γ. In addition to inducing fever, these pyrogens also modulate a large number of host defense responses. After 72 hours, burn patients develop systemic inflammatory response syndrome (SIRS), characterized by tachycardia, relative hypotension, and hyperthermia, which are the classic signs of sepsis that can occur without an infectious source. In fact, body temperature may be as high as 39°C (102.2°F) and the leukocyte count may be as high as 20,000 cells/mL during satisfactory recovery. Thus, elevation of body temperature above normal, leukocytosis, and other signs of inflammation are common among burn patients and should be expected.