The global problem of leprosy may be bigger than recognized, new research suggests. In fact, 40 million individuals around the world require preventive treatment in order to reduce the incidence of leprosy or Hansen’s Disease by 90% in 22 years. 

The new research by NLR (until No Leprosy Remains), and Erasmus University MC, published in PLOS Neglected Tropical Diseases, used mathematical modeling to predict the impact of a combined approach of contact screening and provision of post-exposure prophylaxis (PEP) on new cases of leprosy and to estimate the number of contacts requiring PEP at a global and country level for 25 years. 

“This study provides important insight into the challenge that remains to reach zero leprosy. It quantifies the actual numbers of contacts that would need to be reached with post-exposure prophylaxis over time and the effort and workload it represents. This estimation is based on the best scientific methodology we have at present to produce such numbers,” says Co-author Professor Jan Hendrik Richardus of Erasmus MC. “It should not be interpreted as a precise calculation, but as an order of magnitude exercise to direct policy development in leprosy control and elimination.”

About 80% of all new leprosy patients are detected and reported in India, Brazil, and Indonesia. In these three countries, 33 million people would need to be treated with PEP. The time to reach a 90% reduction in new cases, however, could be shortened if more effective strategies for early diagnosis are implemented, such as extending the number of contacts provided with PEP, a second dose of treatment after 2 years, or the use of a diagnostic test to identify early infection in combination with providing an enhanced PEP regimen.

For most of the 110 countries where leprosy has been reported and transmission is probably still ongoing, the researchers also predict that a reduction of 50% of new cases could be achieved at global level in 5 years if around 21 million people are treated with preventive treatment.