What is leprosy?
Leprosy, also known as Hansen’s disease, is a chronic infectious disease caused by Mycobacterium leprae. The disease mainly affects the skin, the peripheral nerves, mucosal surfaces of the upper respiratory tract and the eyes. Leprosy is known to occur at all ages ranging from early infancy to very old age. Leprosy is curable and early treatment averts most disabilities.
The exact mechanism of transmission of leprosy is not known. At least until recently, the most widely held belief was that the disease was transmitted by contact between cases of leprosy and healthy persons. More recently the possibility of transmission by the respiratory route is gaining ground. There are also other possibilities such as transmission through insects which cannot be completely ruled out.
Signs/symptoms and diagnosis
Clinical signs are easy to observe. In a country or area with a high incidence of leprosy, an individual should be regarded as having leprosy if he or she shows ONE of the following cardinal signs:
- skin lesion consistent with leprosy and with definite sensory loss, with or without thickened nerves
- positive skin smears
The skin lesion can be single or multiple, usually less pigmented than the surrounding normal skin. Sometimes the lesion is reddish or copper-coloured. A variety of skin lesions may be seen but macules (flat), papules (raised), or nodules are common. Sensory loss is a typical feature of leprosy. The skin lesion may show loss of sensation to pin pick and/or light touch. Thickened nerves, mainly peripheral nerve trunks constitute another feature of leprosy. A thickened nerve is often accompanied by other signs as a result of damage to the nerve. These may be loss of sensation in the skin and weakness of muscles supplied by the affected nerve. In the absence of these signs, nerve thickening by itself, without sensory loss and/or muscle weakness is often not a reliable sign of leprosy.
Epidemiological situation, burden and distribution
According to official reports received from 138 countries from all WHO regions, the global registered prevalence of leprosy at the end of 2015 was 176 176 cases (0.2 cases per 10 000 people). The number of new cases reported globally in 2015 was 211 973 (2.9 new cases per 100 000 people). In 2014, 213 899 new cases were reported, and in 2013, 215 656 new cases.
The number of new cases indicates the degree of continued transmission of infection. Global statistics show that 199 992 (94%) of new leprosycases were reported from 14 countries reporting more than 1000 new cases each and only 6% of new cases were reported from the rest of the world.
Pockets of high endemicity still remain in some areas of many countries, including countries reporting less than 1000 new cases. Some of these areas show very high notification rates for new cases and may still witness intense transmission.
Monitoring and evaluation
WHO collects data on leprosy annually between April and June using the following variables:
- the prevalence of leprosy (defined as the number of patients on treatment at a particular point of time, usually 31 December)
- new cases detected
- treatment completion
Since 2015, the following information has been requested: number of children with visible deformities – also called grade-2 disabilities (G2D), at the time of diagnosis; number of foreign-born patients and countries; and whether any discriminatory laws against persons affected by leprosy are present and enacted.
Leprosy is curable with a combination of drugs known as multidrug therapy (MDT), as the treatment of leprosy with only one antileprosy drug (monotherapy) will result in development of drug resistance to that drug. The combination of drugs used in the MDT depends on the classification of the disease. Rifampicin, the most important antileprosy medicine, is included in the treatment of both types of leprosy. For the treatment of patients with multibacillary leprosy, WHO recommends a combination of rifampicin, clofazimine and dapsone; for patients with paucibacillary leprosy, MDT uses a combination of rifampicin and dapsone.
Access to treatment
Multidrug therapy (MDT), first recommended by a WHO Expert Committee in 1984, rapidly became the standard treatment of leprosy and has been supplied by WHO free of charge to all endemic countries since 1995.
As a major supplier of very close to 100% of global MDT needs, WHO works closely with donors and manufacturers to plan the manufacture, procurement and shipment of the MDT drugs having the maximum available shelf life, at the time most appropriate for each national programme. WHO also arranges independent laboratory testing of the drugs at the manufacturer’s own expense in order to ensure that the finished WHO product is the best available for national programmes. Such testing is considered essential to maintain the confidence of national programmes in the donated product.
In order to meet emergency requests for MDT, WHO maintains at the donor’s expense, substantial buffer stocks at the manufacturing plant. Currently these buffer stocks are equivalent to around 40% of global annual requirements but vary depending on perceived need. To ensure a rapid response to requests for smaller emergency supplies, WHO maintains additional buffer stocks at its headquarters in Geneva and Regional Office in Manila. Response times from WHO Geneva are typically 48 hours and most despatches are made via courier.
The Global Leprosy Strategy
In 2016 WHO launched the Global Leprosy Strategy 2016–2020: Accelerating towards a leprosy-free world, which aims to reinvigorate efforts to control leprosy and avert disabilities, especially among children still affected by the disease in endemic countries.
The strategy emphasizes the need to sustain expertise and increase the number of skilled leprosy staff, improve the participation of affected persons in leprosy services and reduce visible deformities as well as stigmatization associated with the disease. It also calls for renewed political commitment and enhanced coordination among partners while highlighting the importance of research and improved data collection and analysis.
The key interventions needed to achieve the targets include:
- detecting cases early before visible disabilities occur, with a special focus on children as a way to reduce disabilities and reduce transmission;
- targeting detection among higher risk groups through campaigns in highly endemic areas or communities; and
- improving health care coverage and access for marginalized populations.
Endemic countries need to include other strategic interventions in their national plans to meet the new targets, namely:
- screening all close contacts of persons affected by leprosy;
- promoting a shorter and uniform treatment regimen; and
- incorporating specific interventions against stigmatization and discrimination