Bangladeshi man and cows
Photo credit: Lepra

About Leprosy (Hansen’s disease)

Leprosy, also known as Hansen’s disease, is caused by Mycobacterium leprae and transmitted via droplets through the nose and mouth of untreated patients. After infection, it can take up to 20 years before symptoms begin to appear.

Since 1981, more than 16 million leprosy patients have been treated with multidrug therapy (MDT), donated at first by The Nippon Foundation, and since 2000 by Novartis, through the World Health Organization. This has reduced the global number of people being treated for M. leprae infection by 99%. However, the number of people newly diagnosed with leprosy has plateaued at more than 200,000 per year for over a decade. The majority of new leprosy cases occur in India, Brazil and Indonesia where diagnosis is often delayed by limited access to health services or fear of stigma and discrimination.

This has a significant impact on both individuals and society, often forcing people to abandon their profession, lose their source of income and limit access to health services and social entitlements.

WHO’s Leprosy Fact SheetILEP’s Leprosy Q&A


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Peter Steinmann, Steven G Reed, Fareed Mirza, T Déirdre Hollingsworth, Jan Hendrik Richardus. Innovative tools and approaches to end the transmission of Mycobacterium leprae. Lancet Infect Dis 2017; 17: 298–305

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Richardus, J. H., Nicholls, P. G., Croft, R. P., Withington, S. G., & Smith, W. C. S. (2004). Incidence of acute nerve function impairment and reactions in leprosy: a prospective cohort analysis after 5 years of follow-up. International journal of epidemiology, 33(2), 337-343. Available at:

World Health Organization, Leprosy factsheet. Available at: