Introduction 

Leprosy is a chronic infectious condition caused by a bacterium called Mycobacterium leprae.¹ There are two main types of leprosy, depending on the bacterial count. Paucibacillary Leprosy usually has milder symptoms and is considered less contagious. Patients with this diagnosis would present with mild muscle weakness and patches of reddish skin. Multibacillary leprosy can cause widespread sores and is considered more contagious. This would also affect nerves, skin, and organs to a greater extent.² It is important to note that if left untreated, paucibacillary leprosy can progress into the multibacillary form.³

Leprosy is transmitted via droplets from the nose and mouth, as the bacteria reside in the upper airways. Frequent and close contact is necessary to transmit the bacteria between people, as leprosy is not considered a highly contagious disease, with around 95% of the population having a natural resistance to the disease.⁴ Leprosy is a global health concern, due to the fact that if not treated early, it can cause disability. Since the 1960s, the World Health Organisation (WHO)  has had a grading system in order to classify the damage that leprosy can cause.⁵ Leprosy also has a long incubation period of 2-8 years (but can extend up to 20 years), meaning that infected individuals may remain asymptomatic (not show any symptoms)  and unknowingly spread the bacteria for years.6 Due to its history, leprosy also has a negative stigma attached, which can lead to individuals being socially excluded. By eliminating leprosy, there is a reduced disease burden on governments and charities, as well as preventing disabilities. The global leprosy campaign spearheaded by organisations such as the WHO has massively reduced cases, but there are still many challenges in surveillance and tackling stigma to ensure the well-being, both physically and mentally, of those with leprosy.   

History and successes 

 Leprosy has been prevalent around the globe for thousands of years. Previous treatment of the disease has included social seclusion, with the formation of leper colonies or in public sanatoriums. These were set up primarily to prevent the disease from spreading, rather than focusing on the treatment of patients. Since ancient times, there has been an association of those with leprosy as being immoral, unclean, or untrustworthy. This helps perpetuate the stigma that still exists today.  Since 1954, the WHO has had the goal of eliminating leprosy. The definition of eradication is that there is one case per 10,000 inhabitants.⁷ In 1982, the WHO endorsed the use of multidrug therapy (MDT) to better treat cases of leprosy. This combined oral antibiotic treatment of Dapsone, Rifampicin, and Clofazimine was able to better target the condition than the monotherapy of Dapsone that was common before. It was so successful that it reduced the prevalence of leprosy worldwide by 86% since 1985.⁸ The medication is free to all who need it, funded by the Nippon Foundation until 2000, when Novartis took over. For someone diagnosed with paucibacillary leprosy, the prescribed treatment runs for 6 months, whilst those with multibacillary leprosy have a 12-month course.⁹ Occasionally, other medications such as pefloxacin or ofloxacin might be used alongside traditional MDT.¹⁰ In 1991, the WHO set the goal to eliminate leprosy as a public health problem by 2000. This was achieved in 112 of the 122 countries in which leprosy was considered endemic.¹¹ As discussed previously, the introduction of MDT helped treat patients much better than previous medications. This, combined with increased awareness of the disease, helped lead to a reduced prevalence of the disease to 1 in 10,000 inhabitants. The first country to be declared leprosy-free was Jordan in 2024, as it has not had any new cases in the past two decades.¹²

Remaining challenges 

Leprosy is still an issue today. There are around 200,000 new cases per year, with 80% of those occurring in Brazil, India, or Indonesia. In order to bring down these numbers in these particular countries, it is important to recognise why they struggle with such a high number of cases per year. Often, there are healthcare delays that can lead to a grade II disability forming in 14% of new cases. In addition to delays occurring from a lack of healthcare support, patients might be reluctant to seek help. This can come from the beliefs that surround someone who has the disease. Previously, there has been the incorrect notion that someone suffering from leprosy must be unclean and immoral.¹³ This can then cause someone to be unwilling to seek help, meaning that the disease can progress until it is too late to prevent permanent damage. COVID-19 also prevented patients from accessing healthcare. Whilst clinics remained open for those with leprosy, it was not as large a global concern during the pandemic.¹⁴ It has been shown that during COVID-19, there was a drop in active case finding as well as a drop in those who came in for treatment. Finally, another issue with trying to treat leprosy is drug resistance. This occurs when the bacteria can resist the antibiotics and continue to grow while the patient is taking medication. For leprosy, the drug resistance rate is around 10.2%.¹⁵ Often, resistance is found when there is non-compliance with MDT (a patient stops taking their medication or takes it incorrectly) or with antimicrobial resistance.  Resistance is more common in relapse cases,¹⁶ which is when symptoms reappear after 1 year and happens in only 1% of all cases.

The future 

India has launched the National Leprosy Elimination Program (NLEP), which is a scheme focused on targeting leprosy, reducing the disease burden, and improving awareness around leprosy and its treatability.¹⁷ It aims to do this through integrating services into the health system, as well as using digital platforms in order to track cases and prevent their spread. The WHO has also recently launched its new strategy to target leprosy, focusing on the years 2021 to 2030. This strategy has four pillars: implementing country-specific roadmaps in endemic countries, scaling up prevention measures, managing ongoing cases, preventing new disabilities, and combating stigma.¹⁸ Another promising sign for the eradication and speedy treatment of those with leprosy is emerging technology, which allows contact tracing to be carried out by health services. This means that a single dose of rifampicin can be administered as a post-exposure prophylaxis (medication administered after a potential exposure to prevent an infection from occurring). This greatly reduces the chance of new cases arising, as they are prevented before the bacteria can take hold.¹⁹

Summary 

Overall, leprosy cases and the severity of each case have been greatly reduced. This is due to the advancement in medication as well as a stigma reduction, which would have previously prevented patients from seeking treatment. Now that the medical community aims to cure those with leprosy instead of just preventing transmission to others, the severity of each case is less, and the chance of developing lifelong disabilities is reduced. Whilst there still remain a few parts of the globe that have a higher rate of new cases, the overall prevalence of leprosy has greatly reduced in the past 50 years.