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Microbiology and Epidemiology
Tularemia is the only disease caused by Francisella tularensis, a small, gram-negative, aerobic bacillus that is a potential agent of bioterrorism.
- Human infection occurs via interaction with biting or blood-sucking insects (especially ticks and tabanid flies in the spring and summer), wild or domestic animals (e.g., wild rabbits, squirrels), or the environment.
- The organism gains entry into the skin or mucous membranes through bites or inapparent abrasions or is acquired via inhalation or ingestion.
- As few as 10 organisms can result in infection when injected into the skin or inhaled; >108 organisms are required to produce infection via the oral route.
- More than half of U.S. cases occur in Arkansas, Oklahoma, and Missouri.