In severe cases, the patient becomes delirious or comatose. The fever lasts between two and three weeks. If untreated, various complications may develop, such as pneumonia, brain damage, heart damage, and death. Immediate treatment with the specific antibiotics tetracycline, doxycycline, or chloramphenicol usually produces rapid improvement. Penicillin-type antibiotics are of no help.
Hospitalization is necessary in severe cases.