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Colorado tick fever pericarditis.

To the Editor.— Colorado tick fever is an acute febrile illness of man caused by an arbovirus transmitted by ticks common to the mountain areas of the northwestern United States, recognized as a distinct entity since Becker's description in 1930.1Experimental studies have shown the laboratory illness to be little varied from the natural disease, including the classically described headache, myalgia, fever, prostration, and leukopenia.2Laboratory-acquired tick fever with complicating pericarditis has not been previously reported in man (C. M. Eklund, personal communication) despite a known association with myocarditis in laboratory animals.3 Report of a Case.— This 60-year-old virology laboratory research assistant with fever, fatigue, and backache of two days' duration had been working with a variety of arboviral agents preceding his illness. Ten days before the onset, he cut his finger while removing brain tissue from a mouse infected with tick fever virus. Marked fatigue and