Q fever is an infectious disease that is spread by the inhalation or ingestion of a bacterium known as Coxiella burnetii, which belongs to the order of Legionellales. C. burnetii is spread mainly by breathing contaminated air or eating or drinking a contaminated food. Farm workers, especially those who work with animals, people who work in slaughterhouses and veterinarians are especially vulnerable to this disease. Because infection can occur as a result of airborne transmission and the agent is very resistant to environmental conditions, it was included on the list of possible bacteriological weapons. Q fever causes highly variable diseases ranging from acute (often self-limited) infection to fatal chronic infection. Infections that do not cause outward symptoms (subclinical) or no symptoms (asymptomatic) are also common.

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