Typhus refers to a series of different diseases caused by a group of bacteria known as Rickettsia. It is usually transmitted by lice and fleas, often from infected rats. Symptoms of mild typhus (endemic typhus and murine typhus) include headaches, fever, nausea, fatigue and a red rash. Severe typhus (epidemic typhus) produces the same symptoms to a greater degree, and may also cause delirium. Untreated, epidemic typhus causes death in 10% to 60% of victims, depending on age and general health.