Ehrlichiosis is a tick-borne disease caused by a bacteria. It is found primarily in the southeastern and south central regions of the United States. The symptoms of the disease usually include fever, muscle aches, weakness and headache. Patients may also experience confusion, nausea, vomiting and joint pain. Signs and symptoms typically begin within 1-2 weeks after the bite of an infected tick. It may occasionally be life-threatening or fatal, depending on the circumstance.