Lyme disease

Lyme disease, also termed Lyme borreliosis, is an infectious disease caused by gram-negative spirochete bacteria belonging to the Borrelia burgdorferi sensu lato species complex. The causative agents are transmitted to humans through the bite of infected hard-bodied ticks in the genus Ixodes. Eight Borrelia species have been identified as pathogenic to humans, including B. mayonii in North America and B. burgdorferi sensu stricto, B. afzelii, B. garinii, B. spielmanii, and B. lusitaniae in Eurasia.

The hallmark early manifestation is erythema migrans, an expanding red rash appearing at the tick bite site approximately one week post-exposure in approximately 70-80% of infected individuals. This rash typically expands gradually, reaching diameters of 5-70 cm, and is usually neither painful nor pruritic. Early disseminated disease may present with fever, headache, fatigue, and in 10-20% of untreated cases, multiple secondary skin lesions. Neurological involvement, termed neuroborreliosis, occurs in roughly 10-15% of untreated patients and typically manifests 4-6 weeks post-infection as lymphocytic meningitis, cranial neuritis, or radiculopathy. Late disseminated infection commonly presents as Lyme arthritis affecting large joints, particularly the knee, occurring in up to 60% of untreated individuals, sometimes months after initial infection.

Lyme disease is the most frequently reported tick-borne illness in the Northern Hemisphere, with endemic regions concentrated in northeastern and north-central United States, as well as in temperate areas of Europe and Asia. Seasonal transmission patterns align with tick life stages, with human infections peaking from May through September in the Northern Hemisphere when nymphal Ixodes ticks are most active and difficult to detect due to their small size. The disease distribution reflects the geographic range of competent tick vectors and reservoir hosts, with regional variation in predominant Borrelia species and associated clinical presentations.

Human infection occurs through the bite of infected Ixodes ticks, commonly known as blacklegged or deer ticks, which acquire Borrelia bacteria by feeding on infected vertebrate reservoir hosts such as small mammals and birds. Transmission typically requires the tick to remain attached for 36-48 hours, as the spirochetes migrate from the tick's midgut to its salivary glands. The nymphal stage of Ixodes ticks is responsible for the majority of human cases due to their small size, high feeding rates during spring and summer, and tendency to feed on humans who may not notice or remove them promptly.

Individuals with frequent or prolonged outdoor exposure in endemic areas face elevated risk, including those engaged in occupational activities such as forestry, landscaping, wildlife management, and outdoor recreation. Children and adolescents show higher incidence rates in some endemic regions, potentially reflecting behavioral factors and outdoor activity patterns. Source-backed detail regarding specific high-risk demographic groups beyond outdoor exposure is not yet available from the provided sources.

Primary prevention centers on avoiding tick bites through protective measures including use of repellents containing DEET or permethrin-treated clothing, performing regular tick checks after outdoor exposure in endemic areas, and prompt removal of attached ticks using fine-tipped tweezers. Landscape management strategies such as creating tick-safe zones by clearing tall vegetation and leaf litter around residential areas may reduce tick exposure risk. Source-backed detail regarding vaccine availability is not yet available from the provided sources.

Surveillance for Lyme disease relies on clinician recognition of characteristic clinical presentations, particularly erythema migrans, combined with epidemiological history of potential tick exposure in endemic areas. Laboratory confirmation through serological testing for Borrelia-specific antibodies supports diagnosis, particularly in disseminated disease stages, though antibody detection may be unreliable during early infection. Monitoring trends requires integration of clinical reporting with laboratory data, accounting for regional variation in diagnostic practices and reporting completeness.

1. 1 WHO Fact Sheet. Detail.
2. 2 WHO Q&A. News.
3. 3 Wikidata. Lyme disease.
4. 4 Wikipedia. Lyme disease - Wikipedia.

ICD-10

ICD-11

Total cases

106K

Peak month

2015-05

Coverage

2 reporting countries · 2012-09-14 → 2016-12-31