Q Fever is a disease of humans and ruminants (cattle, sheep, goats) caused by bacteria called Coxiella burnetii. Most infected animals do not show signs of illness but can shed large amounts of bacteria in the placenta, aborted fetuses, or other reproductive tissues expelled while giving birth. Q fever bacteria are extremely hardy and resistant to many disinfectants; infectious bacteria can remain in the environment for weeks or months. Exposure to just a few bacteria can lead to infection in humans. Most persons infected with the Q fever bacteria experience no illness or flu-like symptoms (fever, chills, headache), but pneumonia and hepatitis can be seen in elderly or debilitated patients. Q fever patients with pre-existing heart conditions may develop chronic infection of the heart valves.

Mild Q fever usually does not require treatment, but weeks or months of antibiotics may be prescribed for patients with heart involvement.

Individuals who have frequent contact with ruminants, including veterinarians, slaughterhouse workers, and sheep and dairy farmers, are at higher risk. The risk of Q fever may be reduced by avoiding direct and indirect contact with the reproductive tissues and fluids of ruminants. ​ ​​