General Information: This subspecies is virulent in humans, and the strain is a clinical isolate that is also virulent in an animal model. Originally isolated from a human case of tularemia in 1951. There are a large number of insertion sequences including a mariner element, which is a transposon typically found in eukaryotes and is the first instance of this element to be found in a microbe, which may have acquired it during transit through one of the insect vectors. Causative agent of tularemia. 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.