Rickettsial infections respond promptly to early treatment with the antibiotics doxycycline (preferred) or chloramphenicol. These antibiotics are given by mouth unless people are very sick. In such cases, antibiotics are given intravenously. Most people noticeably improve in 1 or 2 days, and fever usually disappears in 2 to 3 days. People take the antibiotic for a minimum of 1 week—longer if the fever persists. When treatment begins late, improvement is slower and the fever lasts longer. If the infection is untreated or if treatment is begun too late, people may die, especially if they have epidemic typhus, scrub typhus, or Rocky Mountain spotted fever.