Human infection with Coxiella burnetii is acquired by which route?

• A. Inhalation of infectious material
• B. The bite of a mite (chigger)
• C. The bite of a body louse
• D. The bite of the arthropod Phlebotomus

Answer: (A)

Coxiella burnetii is shed in large numbers in birth products and other contaminated animal materials, and it remains easily aerosolized in dust. Humans become infected when they inhale these aerosols, allowing the bacteria to reach the lungs and establish infection. This inhalation route explains why Q fever is classically associated with contact with livestock or exposure to birthing areas, barns, or dust from farms. While ingestion of unpasteurized milk can occur, it is not the primary route. Bites from mites, lice, or other arthropods are not typical transmission modes for Coxiella burnetii, and those vectors are associated with other pathogens.