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[Gr. typhos, fever]
Any of several rickettsial infections transmitted to humans by lice, fleas, or mites. The causative microbe invades the lining of blood vessels and smooth muscle cells, causing widespread vasculitis. The most common causes of typhus are Rickettsia prowazekii, R. typhi, and Orientia tsutsugamushi. R. prowazekii causes the epidemic typhus found in crowded conditions with poor sanitation, e.g., refugee camps.
The disease may be mild, marked only by a flat rash that spreads out from the trunk and petechiae or by flulike symptoms. In more severe cases, patients have fever, skin necrosis, and gangrene on the tips of the fingers, toes, earlobes, and penis as a result of thrombus formation in blood vessels; focal inflammation and thrombosis in organs throughout the body, including the brain, produce organ-specific signs. Rickettsial infections are diagnosed by identifying the organism through immunofluorescent staining.
Typhus is treated with doxycycline for 7 days.
Bronchopneumonia occurs more frequently than lobar pneumonia. Hypostatic congestion of the lungs, nephritis, and parotid abscess also may occur.
The prognosis is variable. Mortality may be quite high in epidemic typhus and almost nonexistent in murine typhus. Broad-spectrum antibiotics are life-saving if given early enough.