Leprosy

Leprosy is a chronic infectious disease principally caused by Mycobacterium leprae, and also linked to Mycobacterium lepromatosis, that primarily involves the skin, peripheral nerves, upper respiratory tract mucosa, and eyes ^[1][2][3][4]. It is classified as a neglected tropical disease and is clinically diagnosed, with host immune response shaping its polymorphic neurocutaneous manifestations ^[1][3][4].

The disease commonly presents with skin lesions that differ in pigmentation from surrounding skin and show definite loss of sensation, alongside thickened or enlarged peripheral nerves with sensory loss or weakness ^[2]. Clinical phenotypes range from paucibacillary forms with strong inflammatory immunity and few bacteria to multibacillary forms with many bacteria and high non-protective antibody levels ^[3]. Peripheral neural damage may cause sensory and motor deficits as well as hand and foot deformities, and inflammatory leprosy reactions can exacerbate signs and symptoms ^[4].

Leprosy, also known as Hansen disease, is a chronic infectious disease caused mainly by Mycobacterium leprae ^[1]. It is a neglected tropical disease (NTD) which still occurs in more than 120 countries, with around 200 000 new cases reported every year ^[1]. Elimination of leprosy as a public health problem (defined as prevalence of less than 1 per 10 000 population as per World Health Assembly resolution 44.9) was achieved globally in the year 2000 and in most countries by the year 2010 ^[1]. As per data of 2024, Brazil, India and Indonesia continue to report more than 10 000 new cases, while 12 other countries (Bangladesh, Democratic Republic of the Congo, Ethiopia, Madagascar, Mozambique, Myanmar, Nepal, Nigeria, Philippines, Somalia, Sri Lanka and the United Republic of Tanzania) each reported 1000–10 000 new cases; fifty-five countries reported 0 cases and 117 reported fewer than 1000 new cases ^[1].

The infection is believed to spread through inhalation of droplets from the nose and mouth of untreated cases following prolonged close contact ^[1][2]. Casual contact such as handshaking, hugging, or sharing meals does not transmit the disease, and patients cease being infectious after starting treatment ^[1][2].

Reliance on case detection and multidrug therapy alone has not sufficed to interrupt transmission, so WHO recommends screening of household, neighbourhood, and social contacts with single-dose rifampicin as post-exposure prophylaxis ^[1]. National programmes should prioritize early case finding and consider post-exposure prophylaxis for close contacts to prevent progression and reduce nerve damage ^[3]. WHO also provides technical support and coordinates the global strategy toward zero leprosy with prevention and control components ^[1].

1. 1 World Health Organization. Leprosy [Internet]. cited 3 Sept 2026. Available from: https://www.who.int/news-room/fact-sheets/detail/leprosy
2. 2 World Health Organization. Leprosy (Hansen disease) [Internet]. cited 3 Sept 2026. Available from: https://www.who.int/health-topics/leprosy
3. 3 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/
4. 4 Froes LAR Junior et al. Leprosy: clinical and immunopathological characteristics. An Bras Dermatol. 2022 May-Jun. PMID: 35379512. doi: 10.1016/j.abd.2021.08.006. PubMed: https://pubmed.ncbi.nlm.nih.gov/35379512/
5. 5 Makhakhe L et al. Leprosy review. S Afr Fam Pract (2004). 2021 Oct 29. PMID: 34797098. doi: 10.4102/safp.v63i1.5311. PubMed: https://pubmed.ncbi.nlm.nih.gov/34797098/