WHO | Leprosy

Fact sheet N°101
Revised August 2009

Leprosy

Leprosy is a chronic disease caused by a bacillus, Mycobacterium leprae.
M. leprae multiplies very slowly and the incubation period of the disease is about five years. Symptoms can take as long as 20 years to appear.
Leprosy is not highly infectious. It is transmitted via droplets, from the nose and mouth, during close and frequent contacts with untreated cases.

Leprosy mainly affects the skin and nerves.
If untreated, there can be progressive and permanent damage to the skin, nerves, limbs and eyes.

Leprosy was recognized in the ancient civilizations of China, Egypt and India.
The first known written mention of leprosy is dated 600 BC.
Throughout history, the afflicted have often been ostracized by their communities and families.

Leprosy is a curable disease and treatment provided in the early stages averts disability.
With minimal training, leprosy can be easily diagnosed on clinical signs alone.
A WHO study group recommended multidrug therapy (MDT) in 1981. MDT consists of three drugs: dapsone, rifampicin and clofazimine. This drug combination kills the pathogen and cures the patient.
MDT is safe, effective and easily administered under field conditions. MDT is available in convenient monthly calendar blister packs to all patients.
Since 1995, WHO provides free MDT for all patients in the world, initially through the drug fund provided by the Nippon Foundation and since 2000, through the MDT donation provided by Novartis and the Novartis Foundation for Sustainable Development.

PB patients treated with MDT are cured within six months.
MB patients treated with MDT are cured within 12 months.
Patients are no longer infectious to others after the first dose of MDT. In other words, transmission of leprosy is interrupted.
There are virtually no relapses, i.e. recurrences of the disease after treatment is completed.
No resistance of the bacillus to MDT has been detected.
WHO estimates that early detection and treatment with MDT has prevented about four million people from being disabled. This suggests great cost-effectiveness of MDT as a health intervention, considering the economic and social loss averted.

The first breakthrough occurred in the 1940s with the development of the drug dapsone, which arrested the disease. But the duration of the treatment of leprosy was many years, even a lifetime, making it difficult for patients to follow.
In the 1960s, M. leprae started to develop resistance to dapsone, the world’s only known anti-leprosy drug at that time.
Rifampicin and clofazimine, the other two components of MDT, were discovered in the early 1960s.

In 1991 World Health Assembly passed a resolution to eliminate leprosy as a public health problem by the year 2000. Elimination of leprosy as a public health problem is defined as a prevalence rate of less than one case per 10 000 persons; the target was achieved on time.
The widespread use of MDT has reduced the disease burden dramatically.
Over the past 20 years, more than 14 million leprosy patients have been cured about 4 million since 2000.
The prevalence rate of the disease has dropped by 90% – from 21.1 per 10 000 inhabitants to less than 1 per 10,000 inhabitants in 2000.
A dramatic decrease in the global disease burden: from 5.2 million in 1985 to 805 000 in 1995 to 753 000 at the end of 1999 to 286 000 cases at the end of 2004.
Leprosy has been eliminated from 113 countries out of 122 countries where leprosy was considered as a public health problem in 1985. An additional 13 countries achieved the elimination target since 2000.
A 20% annual decrease in new cases detected globally since 2001.
Absence of resistance to drugs used in MDT.
Efforts currently focus on eliminating leprosy at a national level in the remaining endemic countries and at a sub-national level from the others.

At the beginning of 2009, cases reported from 121 countries totaled 213 036, while the number of new cases detected during 2008 was 249 007. The number of cases detected globally has fallen by 9 126 (a 4% decrease) during 2008 compared with 2007.
Most previously highly endemic countries have now reached elimination (defined as a registered prevalence rate of <1 case/10 000 population).
Pockets of high endemicity still remain in some areas of Angola, Brazil, Central African Republic, Democratic Republic of Congo, India, Madagascar, Mozambique, Nepal, and the United Republic of Tanzania. These countries remain highly committed to eliminating the disease, and continue to intensify their leprosy control activities.

Political commitment needs to be sustained in countries where leprosy remains a public health problem.
In order to reach all patients, treatment of leprosy needs to be fully integrated into general health services. This is a key to successful elimination of the disease.
Partners in leprosy elimination need to continue to ensure that human and financial resources are made available for the elimination of leprosy.
The age-old stigma associated with the disease remains an obstacle to self-reporting and early treatment. The image of leprosy has to be changed at the global, national and local levels. A new environment, in which patients will not hesitate to come forward for diagnosis and treatment at any health facility, must be created.

The following actions are part of the ongoing leprosy elimination campaign:

ensuring accessible and uninterrupted MDT services available to all patients through flexible and patient-friendly drug delivery systems;
ensuring the sustainability of MDT services by integrating leprosy services into the general health services and building the ability of general health workers to treat leprosy;
encouraging self-reporting and early treatment by promoting community awareness and changing the image of leprosy; and
monitoring the performance of MDT services, the quality of patients’ care and the progress being made towards elimination through national disease surveillance systems.

For more information contact:

WHO Media centre
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