Q fever bacteria (Coxiella burnetii,green rods) inside a cell,computer illustration. Coxiella burnetiiis an obligate intracellular bacterium,meaning that it cannot reproduce outside of its host cell. It is the cause of Q fever,and is thought to be the most infectious agent known,with just one bacterium causing disease. Q fever is a disease present in livestock that can be spread to humans by inhalation of contaminated particles. It causes flu-like symptoms,with fever,malaise,headache and nausea. It can progress to pneumonia,which can be fatal |