infectious disease characterized by sudden onset with fever; headache; sore muscles, bones, and joints; and outbreaks of skin lesions on the chest and back. It is transmitted from one person to another by a body louse harbouring the causative organism, the rickettsial bacterium Rochalimaea (formerly Rickettsia) quintana. There may be one period of fever, or the fever may recur several times at intervals of four to five days. Most persons recover within about two months; there may be relapses, however, and the disease becomes chronic in about 5 percent of the cases. Treatment with chlortetracycline brings permanent relief of the symptoms, but the patient continues to carry rickettsiae and remains infectious for lice. First recognized in 1915, trench fever was a major medical problem during World War I. It reappeared in epidemic form among German troops on the Eastern front during World War II. The control of body lice is the chief means of prevention.