Relapsing fever

Relapsing fever refers to infection due to the relapsing fever group of Borrelia species ^[2]. The source material distinguishes this group from the Borrelia burgdorferi sensu lato complex, which causes Lyme borreliosis, and notes that relapsing fever borreliae comprise more than 20 associated species in one scholarly summary ^[2][3]. The record available here does not provide a more granular organism-by-organism definition beyond this genus-level characterization ^[2][3].

The sources describe relapsing fever as a severe infection and note that presentation varies by species and by transmission form ^[1][2]. Reported characteristic symptoms include high fever with sudden onset, chills, severe headache, muscle and joint pain, drowsiness, photophobia, and cough ^[3]. One review also emphasizes that relapsing fever should be considered in the differential diagnosis of a febrile immigrant or refugee, but it does not provide a broader clinical course description in the available text ^[1]. The sources do not supply details on relapsing patterns, complications, or duration, so source-backed detail on those points is not yet available ^[1][3].

The available evidence indicates historical mortality burden in England before the 20th century, when relapsing fever was among infectious diseases causing thousands of deaths ^[4]. In more recent commentary, relapsing fevers are described as emerging or re-emerging and at the same time neglected in developed countries ^[3]. The body louse-borne form is reported as particularly encountered in the Horn of Africa region due to poor hygiene, and it has been described in several European countries as imported by refugees from that region ^[1]. No reliable source-backed incidence, prevalence, or age-specific distribution is provided in the supplied material ^[4][1][3].

The sources identify two main exposure mechanisms: tick-borne transmission and body louse-borne transmission ^[1][3]. One review adds that soft ticks are the main vector group for relapsing fever borreliae, with Borrelia recurrentis transmitted by lice ^[3]. A separate diagnostic review notes that ticks can carry multiple infectious agents and transmit them during blood feeding, which may complicate the clinical picture ^[2]. The material does not specify additional transmission persistence, environmental reservoirs, or human-to-human spread beyond the louse-associated form ^[1][3][2].

The sources most clearly identify people with recent arrival from endemic or affected regions as important to consider in case finding, particularly immigrants and refugees with fever ^[1]. One review specifically notes imported louse-borne cases among refugees from the Horn of Africa, with poor hygiene cited in that context ^[1]. Beyond these migration- and exposure-associated groups, the supplied sources do not provide a fuller source-backed risk-group profile ^[1][3].

The source material links the louse-borne form to poor hygiene in the Horn of Africa region, implying that hygiene and related public-health conditions are relevant exposure-control considerations ^[1]. More generally, the historical review states that preventive measures, public-health interventions, and changes in behavior have reduced the risk of severe infectious diseases, including relapsing fever, but it does not isolate disease-specific interventions in the supplied text ^[4]. Because the snippets do not enumerate vector-control methods, housing measures, or other specific preventive actions, source-backed detail on those points is not yet available ^[1][4].

For surveillance purposes, relapsing fever should be read as a Borrelia-associated bacterial syndrome that may appear in both tick-borne and louse-borne forms and can overlap clinically with other febrile infections ^[1][2]. The sources support attention to travel or migration-linked importation, particularly among refugees from the Horn of Africa, and to possible vector exposure when interpreting febrile illness clusters ^[1][2]. The disease is also described as neglected yet potentially re-emerging, which supports continued monitoring even when case numbers are not prominently reported ^[3].

1. 1 Hytönen J et al. Relapsing fever. Duodecim. 2016. PMID: 29190046. PubMed: https://pubmed.ncbi.nlm.nih.gov/29190046/
2. 2 Cutler SJ et al. Diagnosing Borreliosis. Vector Borne Zoonotic Dis. 2017 Jan. PMID: 28055580. doi: 10.1089/vbz.2016.1962. PubMed: https://pubmed.ncbi.nlm.nih.gov/28055580/
3. 3 Relapsing fevers. Postępy Mikrobiologii - Advancements of Microbiology. 2018. doi: 10.21307/pm-2018.57.1.041. DOI: https://doi.org/10.21307/pm-2018.57.1.041
4. 4 Mercer A et al. Protection against severe infectious disease in the past. Pathog Glob Health. 2021 May. PMID: 33573529. doi: 10.1080/20477724.2021.1878443. PubMed: https://pubmed.ncbi.nlm.nih.gov/33573529/
5. 5 Relapsing Fevers. Infectious Diseases. 2017. doi: 10.1016/b978-0-7020-6285-8.00131-3. DOI: https://doi.org/10.1016/b978-0-7020-6285-8.00131-3
6. 6 Relapsing Fever. Encyclopedia of Entomology. None. doi: 10.1007/0-306-48380-7_3619. DOI: https://doi.org/10.1007/0-306-48380-7_3619

ICD-10

A68

ICD-11

1C21

Total cases

86

Peak month

2022-10

Coverage

2 reporting countries · 1997-01-01 → 2026-06-20