General Information: This isolate was collected from a gerbil in central Asia. This organism was first identified by Edward Francis as the causative agent of a plague-like illness that affected squirrels in Tulare county in California in the early part of the 20th century. The organism now bears his name. The disease, which has been noted throughout recorded history, can be transmitted to humans by infected ticks or deerflies, infected meat, or by aerosol, and thus is a potential bioterrorism agent. This organism has a high infectivity rate, and can invade phagocytic and nonphagocytic cells, multiplying rapidly. Once within a macrophage, the organism can escape the phagosome and live in the cytosol. It is an aquatic organism, and can be found living inside protozoans, similar to what is observed with Legionella.