A tough, inhaled bacterium of farm animals that causes Q fever — usually a flu-like illness, occasionally a long one. Explore its illustrative 3D model, human context, and sources.
PHAC describes C. burnetii as a pleomorphic, Gram-negative, spore-forming coccobacillus existing in two forms: a small-cell variant with condensed nucleoid filaments and a metabolically active large-cell variant. It is an obligate intracellular pathogen that completes its development cycle in the phagolysosome — the acidic compartment most bacteria avoid. CDC states that these bacteria naturally infect some animals such as goats, sheep and cows, and that people become infected by breathing in dust contaminated by infected animal feces, urine, milk and birth products. PHAC reports that approximately 1 to 10 organisms are required to cause infection, one of the lowest infectious doses recorded for any bacterium, and that Q fever is endemic worldwide except New Zealand.
PHAC describes acute Q fever as rarely fatal, with pneumonia mortality of 0.5 to 1.5%, while chronic infection lasting longer than six months develops mainly in immunocompromised people and is associated with a high mortality rate, principally through endocarditis. CDC calls the chronic form life-threatening and requiring several months of antibiotic treatment. Occupational exposure to goats, sheep and cattle matters more here than contact with other people.
Coxiella burnetii · A representative large-cell variant. Its compact small-cell variant is a separate form, not a classical endospore. 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: Coxiella burnetii · pathogen safety data sheet.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.