Leprosy (also known as Hansen’s disease) is a chronic infectious disease caused by bacteria mainly spread through droplets from the nose and mouth of people suffering from untreated leprosy (produced when they sneeze or cough).

Registered cases per 10,000 population – prevalence rates (2016) Only Comoros, Kiribati, the Marshall Islands and Micronesia have more than 2 registered cases per 10,000.

Number of new cases of leprosy reported per year

WHO roadmap target:

Global elimination by 2020

A slight increase in the number of new cases was seen between 2015 and 2016, which may be due to intensified active case detection. The persistent incidence of new cases, a substantial proportion of whom are children, is concerning and indicates that progress towards the interruption of transmission has halted. The concern is exacerbated by the detection of new patients, including children, who already have disabilities caused by leprosy.

The situation varies widely by country, and several that were previously highly endemic are approaching zero incidence.

Treatment of cases and their contacts may become important in stopping transmission but is still in the early stages and in only a limited number of countries.

All requests for drugs in 2015 and 2016 were filled by the manufacturer, which pledged to supply multi-drug therapy for all new cases through 2020. The programme has made progress in supporting morbidity management and social inclusion. The number of countries that reported access to wound care and community rehabilitation for patients living with leprosy-related disabilities has met the targets set for 2016.

There was good progress in global leadership from WHO and collaboration among partners to develop a new global strategy for 2016–2020, with operational guidelines and a monitoring and evaluation framework.

The main problems identified include continued transmission, slow case detection and social exclusion, which not only causes suffering but facilitates transmission by delaying detection of the disease and interrupting treatment.

The main challenge for the programme is the absence of a diagnostic tool; simplified therapy would also be an advantage. A better coordinated research strategy on diagnostics will be critical but will require mobilization of significant resources. Interruption of transmission will be unlikely without good coverage of the population at risk with preventive chemotherapy and/or a vaccine.

Tools are needed to measure infection in order to verify that transmission has been interrupted.

Studies on vaccines and preventive chemotherapy are currently under way. These problems will be addressed through a coordinated strategy for a ‘global partnership for zero leprosy’.

This is part of Reaching a Billion, the fifth progress report of the London Declaration on NTDs. Read the full report.