A rabbit-and-rodent bacterium so infectious that a handful of cells can cause illness, yet it is not passed between people. Explore its illustrative 3D model, human context, and sources.
PHAC describes F. tularensis as a Gram-negative, non-motile coccobacillus, non-sporing and aerobic, requiring cystine for growth, and distinguishes Jellison type A, which is highly virulent, from type B, which causes milder disease. Its infectious dose is extraordinarily low — PHAC gives 5 to 10 organisms by the respiratory route against 10⁶ to 10⁸ by ingestion. CDC states that people become infected through tick and deer fly bites, skin contact with infected animals, drinking contaminated water, and inhaling contaminated aerosols or agricultural and landscaping dust, and that naturally occurring infections have been reported from all states except Hawaii. Human-to-human transmission is rare.
PHAC gives a 5 to 15% fatality rate for type B strains and approximately 35% mortality from pulmonary tularemia caused by type A strains, and notes that fever lasts 3 to 6 weeks without treatment. The extremely low respiratory infectious dose of 5 to 10 organisms is why this organism is handled at high containment in laboratories, but it is rare and is not spread between people.
Francisella tularensis · A short oval coccobacillus. An unsourced capsule-like layer is deliberately omitted. This is a species-informed teaching diagram; colours, proportions, envelope spacing and internal detail are illustrative. The model uses muted illustrative colours; stains, colony pigments and microscopy colourization are not natural cell colours. Anatomy is enlarged for phone viewing. Morphology reference: Francisella tularensis · pathogen safety data sheet.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.