Leprosy is a slowly progressive, bacterial infection that mainly affects the skin and peripheral nerves. It affects all ages and both sexes. It is easily treated with multidrug therapy (MDT). If untreated, progressive and permanent infection can damage the skin, nerves, limbs and eyes. Leprosy is an important cause of permanent disability in the world. Underserved and marginalized communities are most at risk. Historically, affected people have been subject to discrimination, stigmatisation and exclusion.


  • definite loss of sensation in a pale (hypopigmented) or reddish skin patch
  • thickened or enlarged peripheral nerve, with loss of sensation or weakness of muscles supplied by that nerve
  • presence of acid-fast bacilli in a slit skin smear.

Infectious Agents

The infectious agent is the bacterium Mycobacterium leprae.

Mode of transmission

Leprosy is not highly infectious. The exact mode of transmission is unknown. The disease is thought to be transmitted by air through droplets from the nose and mouth, during close and frequent contacts with untreated cases.


Prompt diagnosis and treatment prevents disability and impedes transmission. Thus, early detection and prompt treatment of cases with MDT is the corner- stone of global leprosy elimination. Health education should promote the avail- ability of effective MDT, and emphasize that that leprosy is easily cured. Early treatment will lead to minimal disabilities and will prevent transmission. Reducing contact with known leprosy patients is of dubious value and can lead to stigmatization


  1. Global leprosy situation, beginning of 2008. Weekly Epidemiological Record, 15 August 2008, Vol.83, 33:293–300. Geneva, World Health Organization (WHO) (Global leprosy situation, beginning of 2008 (who.int)).
  2. Leprosy: Sri Lanka prevalence rate per 10,000. WHO Regional Office for South-East Asia, 2005 (http://www.searo.who.int/EN/Section10/Section20/Section54_12169.htm, accessed 3 September 2010).

Further reading

Leprosy elimination monitoring (LEM): guidelines for monitors (2000). Geneva, WHO, 2000 (Leprosy Elimination Monitoring (LEM) — Guidelines for monitors (who.int)).