Leprosy (Hansen's disease) is a chronic infectious disease caused by Mycobacterium leprae — an exceptionally slow-growing bacterium that primarily affects the peripheral nerves, skin, upper respiratory tract and eyes. It is one of the oldest recorded diseases and has caused more human suffering through stigma than almost any other condition. Despite being entirely curable, it continues to cause preventable disability in the world's most marginalised populations.

How is leprosy transmitted?

M. leprae is transmitted primarily through respiratory droplets (nasal secretions) from untreated multibacillary patients — via prolonged close contact (living in the same household). It is the LEAST contagious of all infectious diseases: approximately 95% of people are naturally immune due to innate cell-mediated immunity. The armadillo is the only known non-human reservoir. Leprosy is NOT transmitted by casual contact, sharing utensils, or touch.

What are the symptoms of leprosy?

Leprosy presents with: hypopigmented or reddish skin patches that are anaesthetic (no sensation to touch, pain or temperature); peripheral nerve thickening (palpable at elbow, wrist, knee, ankle); and muscle weakness in hands and feet. Eye involvement causes lagophthalmos (inability to close the eye fully) — the primary cause of blindness in leprosy. Without treatment: progressive peripheral neuropathy → sensory loss → injuries → secondary infections → tissue destruction → "leonine" facial appearance in lepromatous disease.

Yes — leprosy is entirely curable with multidrug therapy (MDT). A single dose of rifampicin kills 99% of bacteria within hours. The full 6- or 12-month MDT course achieves >99% cure and prevents further disability. Crucially, leprosy is NOT transmissible after the first dose of MDT. The challenge is early diagnosis — before nerve damage causes irreversible disability — and overcoming stigma that delays help-seeking.

What causes leprosy disability?

Leprosy disability arises from peripheral nerve damage — not from the bacteria directly destroying tissue (as commonly misconceived). M. leprae invades Schwann cells in peripheral nerves, triggering immune-mediated nerve inflammation (neuritis). This causes anaesthesia (loss of protective sensation), muscle paralysis and autonomic dysfunction. Anaesthetic hands and feet are then damaged by unnoticed trauma, burns and repeated minor injuries — leading to ulceration, secondary infection and tissue loss.

Who is affected by leprosy?

India accounts for approximately 54% of global cases; Brazil and Indonesia together account for another 25%. Within countries, leprosy disproportionately affects the poorest and most marginalised — rural agricultural communities, tribal populations, slum dwellers and people experiencing homelessness. Children account for approximately 8-10% of cases — child cases indicate ongoing active transmission in communities.

What is leprosy stigma?

Leprosy has carried stigma for millennia — biblical and historical references to "lepers" as untouchable, cursed or sinful. This stigma persists today: patients hide their diagnosis for years (allowing disability to develop); affected people are ostracised from families and communities; many countries have discriminatory laws allowing leprosy patients to be separated from society; and healthcare workers avoid treating leprosy patients. WHO's 2030 roadmap explicitly targets zero discrimination as a core goal.

What is post-exposure prophylaxis for leprosy?

A single 600mg dose of rifampicin given to close contacts (household members, neighbours) of newly diagnosed leprosy patients reduces their risk of developing leprosy by 57% (COLEP trial, Bangladesh). PEP-Plus (rifampicin + BCG booster) shows greater protection. Contact tracing and PEP is a major component of WHO's strategy to break transmission chains. It requires community outreach and contact identification capacity.

Why does leprosy persist despite a cure existing?

The persistence of leprosy despite an effective cure reflects: diagnostic delays (long incubation period 2-10 years + stigma-driven concealment + non-specific early presentation); inadequate contact tracing (not systematically done in most endemic countries); incomplete case detection (estimated 3-4x underreporting); leprosy's absence from primary care training in most endemic countries; and the extreme marginalisation of affected populations. Achieving zero leprosy requires integrating leprosy detection into primary care and addressing social determinants.

What is the BCG vaccine connection?

BCG (Bacillus Calmette-Guérin) vaccination — primarily known for TB prevention — provides partial protection against leprosy (30-80% efficacy depending on region and strain). A second BCG dose provides additional protection. BCG vaccination at birth is therefore part of leprosy prevention strategy in endemic settings. The BCG-plus-rifampicin PEP combination is being evaluated as a more powerful preventive strategy.

How does GMJ News cover leprosy?

GMJ News covers WHO Global Leprosy Reports, Zero Leprosy Roadmap progress, PEP trial results, MDT access and stigma-reduction initiatives. Leprosy elimination is a global NTD priority — the principles of integrated primary care detection and stigma elimination are relevant to PHIG's health equity agenda and the Georgian Medical Journal.

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Leprosy (Hansen's Disease)

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

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Leprosy (Hansen's disease) — caused by Mycobacterium leprae — remains one of the world's most stigmatising diseases, with over 200,000 new cases detected annually across more than 120 countries and an estimated 3-4 million people living with leprosy-related disability (WHO). Despite being entirely curable with multidrug therapy (MDT) — provided free by WHO since 1995 — leprosy persists in Brazil, India, Indonesia and parts of Africa, perpetuated by poverty, delayed diagnosis and persistent social stigma. WHO's Zero Leprosy Roadmap 2021-2030 targets zero new cases with grade 2 disability, zero child cases and zero discrimination.

Key messages

200,000 new cases per year

Leprosy (Hansen's disease) — caused by Mycobacterium leprae — continues to affect over 200,000 people per year across more than 120 countries, with India, Brazil and Indonesia accounting for approximately 80% of cases (WHO 2023).

Entirely curable

Leprosy is entirely curable with multidrug therapy (MDT) — a combination of rifampicin, dapsone and clofazimine, provided free by WHO since 1995. MDT cures leprosy and prevents disability when started before nerve damage.

Nerve damage and disability

The hallmark of leprosy is peripheral nerve damage — causing anaesthesia (loss of sensation) in patches of skin and extremities, muscle weakness and eye complications. Without early treatment, nerve damage progresses to irreversible disability.

Zero Leprosy Roadmap 2030

WHO's Zero Leprosy Roadmap 2021-2030 targets: zero new cases with grade 2 disability; zero child cases; zero countries with laws allowing discrimination based on leprosy. It calls for integrated leprosy services in primary health care and community-based rehabilitation.

Stigma is the biggest barrier

Leprosy-related stigma — rooted in historical misunderstanding of contagion and disfigurement — remains the primary barrier to early diagnosis and treatment. Fear of stigma delays help-seeking by years, allowing preventable disability to occur.

Post-exposure prophylaxis (PEP)

A single dose of rifampicin given to close contacts of leprosy patients (post-exposure prophylaxis, PEP) reduces new leprosy cases by 57% (COLEP trial). PEP-Plus (rifampicin + BCG) shows even greater protection. Scaling PEP is a major WHO 2030 strategy.

Key statistics

200K+

new leprosy cases detected/year

WHO 2023

120+

countries with endemic leprosy

WHO

80%

of cases in India, Brazil, Indonesia

WHO

3M+

living with leprosy-related disability

WHO/ILA

57%

reduction in new cases with PEP

COLEP trial

2030

WHO Zero Leprosy target year

WHO NTD Roadmap

New leprosy cases detected globally 2000-2022 (thousands/year) — WHO

Source: WHO Global Leprosy Report. COVID-19 disrupted detection in 2020; recovery ongoing.

Glossary of key terms

Mycobacterium leprae
WHOThe acid-fast bacillus causing leprosy — grows extremely slowly (doubling time 12-14 days, the slowest of any known bacterium), which explains leprosy's long incubation period (2-10 years). It cannot be cultured in standard media; grows in armadillos and mouse footpads.

Multidrug therapy (MDT)
WHOThe standard leprosy treatment — a combination of rifampicin (kills most bacteria rapidly), dapsone and clofazimine, given for 6 months (paucibacillary) or 12 months (multibacillary). Provided free of charge by WHO. Cure rate >99%.

Grade 2 disability
WHOVisible deformity or damage to eyes, hands or feet caused by leprosy nerve damage — the most serious disability outcome. Indicates advanced disease where prevention of disability is no longer possible. WHO targets zero new grade 2 disability cases by 2030.

Paucibacillary (PB) and multibacillary (MB)
WHOLeprosy classification based on bacterial load: paucibacillary (1-5 skin patches, smear-negative) — less infectious; multibacillary (>5 patches or smear-positive) — more bacterial load, longer treatment course, more disability risk.

Leprosy reactions
WHOImmune-mediated episodes occurring during or after MDT — Type 1 (reversal reaction — T-cell mediated, causing nerve swelling and acute pain) or Type 2 (erythema nodosum leprosum — immune complex mediated). Treated with corticosteroids. Major cause of nerve damage if untreated.

Post-exposure prophylaxis (PEP)
WHO/COLEPSingle-dose rifampicin given to close contacts of newly diagnosed leprosy patients — reduces their risk of developing leprosy by 57% (COLEP trial). PEP-Plus (rifampicin + BCG) shows even greater protection. Major component of WHO's 2030 elimination strategy.

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Leprosy (Hansen's Disease)

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Glossary of key terms

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