Increased levels of macrophage colony-stimulating factor, gamma interferon, and tumor necrosis factor alpha in sera of patients with Orientia tsutsugamushi infection.

Levels of macrophage colony-stimulating factor (nine of nine patients) and gamma interferon (six of nine patients) in serum were elevated above the range of normal in the acute phase of tsutsugamushi disease. Significant increases in levels of tumor necrosis factor alpha were observed during the convalescent phase in five patients, and they exceeded the levels observed during the acute phase. Hypercytokinemia appeared to be responsible for the emergence of the symptoms of tsutsugamushi disease.