Leprosy

Leprosy is an infectious disease attributed to Mycobacterium leprae, with review literature also identifying Mycobacterium lepromatosis as a causative agent ^[1][3]. It is characterized in the source material as a neurological and dermatological disease, reflecting involvement of peripheral nerves and skin ^[3]. The disease is presented as a neglected tropical disease with substantial morbidity in marginalized communities ^[1].

The clinical phenotype of leprosy is described as a spectrum that tracks host immune response, ranging from paucibacillary disease with vigorous pro-inflammatory immunity and few bacteria to multibacillary disease with large bacterial loads and high levels of apparently non-protective anti-M. leprae antibodies ^[1]. The literature also lists indeterminate, tuberculoid, borderline tuberculoid, mid-borderline, borderline lepromatous, and lepromatous forms, as well as type 1, 2, and 3 reaction states ^[3]. M. leprae infects Schwann cells of the peripheral nervous system, supporting the neurological component of disease ^[3]. The source material notes that diagnosis remains clinical, so asymptomatic infection may be missed ^[1].

Leprosy remains endemic in more than 140 countries and was still reporting approximately 200,000 new cases worldwide in 2017 ^[2]. A more recent review states that, before the COVID-19 pandemic, annual new case detection had plateaued for more than a decade at about 200,000 cases ^[1]. The disease causes significant morbidity in marginalized communities ^[1], and migration may introduce cases into nonendemic areas such as North America ^[2]. The sources also note reports of autochthonous transmission in parts of the United States among people without foreign exposure history ^[2].

The provided sources do not give a detailed transmission mechanism for leprosy beyond noting that autochthonous person-to-person transmission has been reported in the United States ^[2]. They also indicate that persons with infection may remain asymptomatic and therefore undetected, which has implications for ongoing spread ^[1]. Source-backed detail on specific routes, environmental persistence, or reservoir ecology is not yet available in the supplied snippets ^[1][2].

The sources identify marginalized communities as experiencing substantial morbidity ^[1]. They also indicate risk related to close contact with affected persons, since post-exposure prophylaxis is specifically suggested for such contacts ^[1]. Additional source-backed detail on age, occupation, or other high-risk groups is not yet available in the supplied snippets ^[1][2].

The reviewed literature emphasizes early case detection and consideration of post-exposure prophylaxis for close contacts of affected persons ^[1]. It also frames these measures as important for interrupting transmission and improving patient outcomes ^[1]. Beyond this, source-backed detail on specific prevention schedules or broader exposure-control measures is not yet available in the supplied material ^[1].

Leprosy surveillance should be interpreted in the context of long incubation, with the cited review giving an incubation period of 2 to 6 years and noting that longer periods have been described ^[1]. Because diagnosis remains clinical and asymptomatic infection may go undetected, routine case counts likely underestimate the full infection burden ^[1]. The literature also suggests that declining clinical expertise and nonendemic introductions can affect recognition and reporting, particularly in regions receiving migration from endemic settings ^[1][2].

1. 1 Grijsen ML et al. Leprosy. Nat Rev Dis Primers. 2024 Nov 28. PMID: 39609422. doi: 10.1038/s41572-024-00575-1. PubMed: https://pubmed.ncbi.nlm.nih.gov/39609422/
2. 2 Maymone MBC et al. Leprosy: Clinical aspects and diagnostic techniques. J Am Acad Dermatol. 2020 Jul. PMID: 32229279. doi: 10.1016/j.jaad.2019.12.080. PubMed: https://pubmed.ncbi.nlm.nih.gov/32229279/
3. 3 Mungroo MR et al. Mycobacterium leprae: Pathogenesis, diagnosis, and treatment options. Microb Pathog. 2020 Dec. PMID: 32931893. doi: 10.1016/j.micpath.2020.104475. PubMed: https://pubmed.ncbi.nlm.nih.gov/32931893/
4. 4 Leprosy. BMJ. 1946. doi: 10.1136/bmj.2.4475.544-b. DOI: https://doi.org/10.1136/bmj.2.4475.544-b
5. 5 Leprosy. The Boston Medical and Surgical Journal. 1904. doi: 10.1056/nejm190412221512502. DOI: https://doi.org/10.1056/nejm190412221512502
6. 6 Leprosy. Organization and Practice in Tuberculosis Bacteriology. 1985. doi: 10.1016/b978-0-407-00296-8.50015-7. DOI: https://doi.org/10.1016/b978-0-407-00296-8.50015-7

ICD-10

A30

ICD-11

1B20

Total cases

957K

Total deaths

15

Peak month

2004-08

Coverage

6 reporting countries · 2000-01-01 → 2026-06-20