Leprosy is a neglected tropical disease (NTD) caused by Mycobacterium leprae. Since the introduction of multidrug therapy (MDT), the registered prevalence has decreased substantially, from more than 5 million cases in the 1980s to 133 802 cases in 2021. New cases continued to occur, however, indicating continuing transmission of infection. Screening of contacts and chemoprophylaxis with single-dose rifampicin were recommended as a crucial step to break the chain of transmission. (1) The Global Leprosy Strategy 2021-2030 (2) was developed as constituent of the NTD road map 2021-2030, (3) with the goal of eliminating leprosy (i.e., interruption of transmission).
Global leprosy situation
WHO collects statistics on leprosy annually from countries to assess the situation and to publish an annual global leprosy update. Paper-based data collection was gradually replaced with a web-based data management system based on the District Health Information System 2 between 2014 and 2017. An abridged Excel[R] sheet was used in low-endemicity settings where very few or even no new autochthonous cases are detected.
In 2021, 143 countries provided statistics, as compared with 127 in 2020: 37 in the African Region (AFR), 27 in the Americas Region (AMR), 21 in the Eastern Mediterranean Region (EMR), 16 in the European Region (EUR), 76 in the South-East Asia Region (SEAR) and 31 in the Western Pacific Region (WPR). Reports were received from all 23 global priority countries. Most countries reported for the calendar year January-December 2021, while a few reported for a different 12-month period (April 2021-March 2022). Rates were calculated per million population according to estimates (medium variant) provided by the United Nations Department of Economic and Social Affairs, World Population Prospects 2022 revision. (4) The population of children ([less than or equal to]15 years) was used as the denominator for calculating child case detection rates.
Globally, the registered prevalence of leprosy (number of cases on treatment at the end of 2021) was 133 802, and the prevalence rate was 16.9 per million population. The number of registered cases at the end of the year was 20 960 (prevalence rate 18.0) in AFR, 25 053 (24.3), in AMR, 4206 (5.5) in EMR, 81 222 (39.4) in SEAR and 2360 (1.2) in WPR.
The numbers of new cases, case detection rates and the proportions of women among new cases are shown in Table 1.
During 2021, 140 594 new cases were reported globally, for a case detection rate of 17.83 per million population. The rate of detection of new cases increased by 10.2% as compared with 2020 (128 405). New cases accounted for 66.5% of cases in SEAR, followed by 15.1% in AFR and 14.1% in AMR (Figure 1); the proportions of new cases in EMR and WPR were low, at 2.6% and 1.8%, respectively. Map 1 shows the distribution of new cases detected in 2021. Of the 142 countries that reported, 36 reported 0 new cases, 58 reported <100 new cases, 36 reported 101-1000 new cases, and 10 countries reported 1001-10 000 new cases. Brazil, India and Indonesia continued to...