Epidemiologic characteristics of human tularemia in the southwest-central states, 1981-1987

From 1981 through 1987, a total of 1,041 cases of tularemia in humans were reported in Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas; this represents 60% of the cases reported in the United States during this same time period. The state of Arkansas reported the highest total (420 cases). Annual incidence rates per one million population ranged from 36.3 in Arkansas to less than 5.0 in Kansas, Louisiana, and Texas. Epidemiologic data were available for 1,026 cases. The majority of cases were white (88%) and male (75%). May, June, and July were the months of onset of symptoms for 52% of the cases. For the cases with known exposure history, 63% reported an attached tick and 23% had exposure to rabbits. Other animals associated with human infection were squirrels, cats, and raccoons. The case-fatality ratio was 2%. Public health efforts to prevent human tularemia cases in the six southwest-central states should focus on reducing exposure to ticks.