The Course of Infection With Coxiella Burneti

Infection with Coxiella burneti has three phases—incubation period, febrile phase and postfebrile phase. The usual range of the incubation period is about 14 to 26 days, with a mean of 19 to 20 days, but may extend to 37 or 60 days. It decreases with increasing dosage. Sartwell's method may indicate whether an outbreak has arisen from single or multiple exposure. In 138 cases the duration of fever was five to 57 days, with a median of 10 days. It tended to increase with age. In 28% the fever relapsed. Focal inflammation of the liver was common. Pneumonitis, frequently reported in overseas cases, is rare in Brisbane. One case was complicated with encephalomyelitis. Rickettsiæ were present in the blood during the fever, but not during the relapse. They were often found in the urine during the fever and also in early convalescence. Four cases in 273 were fatal. After defervescence, rickettsiæ may persist in guinea-pigs, particularly in the kidney, for at least four weeks. They may multiply in the human placenta and heart valves. In human serum, specific agglutinins may persist for a variable period, up to at least five years; complement-fixing antibodies continue much longer.