Overview
Relapsing fever is an infectious disease caused by spirochete bacteria in the genus Borrelia. It is named for the tendency of fever and other symptoms to abate and then recur until the infection is resolved. Historically it has also been called typhinia in older literature.
Causes and transmission
The illness results from infection with several Borrelia species. Some forms are transmitted by body lice, while others are carried by soft ticks. Outbreaks tied to crowded, unhygienic conditions are typically associated with lice-borne strains; tick-borne forms are more often sporadic in areas where infected ticks live. The organisms are blood-borne during symptomatic episodes and can be detected in blood samples.
Symptoms and clinical course
Typical features include abrupt onset of fever, chills, headache, muscle and joint pains, and malaise. These symptoms commonly last several days, then diminish for a symptom-free interval, and later recur — hence the name. Other possible findings are rash, nausea, and enlarged spleen or liver in some patients. Severe complications can occur if the infection is untreated.
Diagnosis and treatment
Diagnosis is usually made by finding the spirochetes in a blood smear during a febrile episode or by molecular and serologic tests. Clinicians treat relapsing fever with appropriate antibiotics; common choices include tetracyclines or penicillins depending on patient factors and local guidance. Treatment can provoke a rapid immune response with transient worsening of symptoms (Jarisch–Herxheimer reaction), which clinicians monitor for and manage supportively.
Prevention and public health
Preventive measures focus on vector control and personal protection: improving hygiene and reducing body-louse exposure, using tick-avoidance strategies, and controlling rodent or tick habitats in endemic areas. Public-health responses to outbreaks often combine treatment of cases with interventions to eliminate lice and improve living conditions.
Notable distinctions and further information
Relapsing fever is often classified as louse-borne (epidemic) or tick-borne (endemic), with different epidemiology and vectors. For clinical details and symptom lists see clinical features, and for laboratory identification and taxonomy see Borrelia bacteria resources. Additional overviews and guidance can be found via general infectious disease references (overview).