Tularemia Epidemic: Vermont, 1968

North America's largest outbreak of tularemia linked to human contact with aquatic mammals occurred in the spring of 1968 in Vermont, a state with no previous reports of tularemia. Forty-seven cases were diagnosed in persons who had trapped or handled muskrats within a four-week period. Investigation revealed a wide spectrum of disease ranging from severe prostrating illness to inapparent infection. Almost all the symptomatic patients had fever and constitutional symptoms. Skin lesions and axillary adenopathy, although present in most symptomatic patients, were variable features. In the 46 patients who had agglutination titers of 1:160 or greater against Francisella tularensis, there was no correlation between titer and presence or absence of symptoms, severity of symptoms, duration of illness or effect of treatment. F. tularensis was identified in the exudate from the skin lesion of one patient. It was also cultured from water, mud, and 5 per cent of the muskrats in the area of most intensive trapping.