Through the Looking Glass: Revisiting the Forgotten Face of Leprosy
This is the first of three posts from participants in Baylor College of Medicine’s National School of Tropical Medicine Summer Institute program.
When my mother was in fifth grade, her school in Karachi, Pakistan, organized a field trip to the Marie Adelaide Leprosy Center. She remembers standing on one side of glass windows, looking in at people who had been isolated for years. Many had been cast out of their homes, turned away from hospitals and abandoned by their family. She is now an infectious disease physician who still carries that memory, one that shaped her commitment to caring for those left behind.
These individuals were isolated because of society’s fear of their illness. To understand how that stigma took hold and endures, it helps to understand the disease itself.
Hansen’s disease, historically known as “leprosy,” is primarily caused by Mycobacterium leprae, a slow-growing bacterium that targets the skin and peripheral nerves. It damages Schwann cells, glial cells responsible for nerve function and regeneration, and can cause sensory loss, neuropathic ulcers, muscle denervation and, if left untreated, lifelong disability.
Despite its reputation, Hansen’s disease is not highly contagious. About 95% of people have natural immunity, and transmission typically requires prolonged close contact, usually via respiratory droplets. In rare cases, zoonotic (animal-to-human) transmission from nine-banded armadillos has been reported in the southeastern United States. Factors like malnutrition and co-infections that weaken the immune system can increase the risk of infection.
What makes Hansen’s disease so elusive isn’t just the bacterium; it’s the delay in detection. The disease has an exceptionally long incubation period, ranging from a few months to 20 years. As a result, individuals may unknowingly carry the infection or live with mild symptoms for years before being diagnosed. Leprosy is classified into two types: paucibacillary (PB), involving five or fewer skin lesions with a low bacterial load, and multibacillary (MB), involving six or more lesions, higher bacterial concentrations and more extensive nerve involvement.
Thankfully, since the 1980s, Hansen’s disease has been curable through multidrug therapy (MDT), which combines rifampicin, dapsone and clofazimine. This combination kills the bacteria, stops transmission and prevents antibiotic resistance seen with earlier monotherapy. PB cases are typically treated with six months of MDT, while MB cases are treated with 12. However, MDT cannot reverse existing nerve damage, making early diagnosis critical to preventing lifelong disability.
In recent decades, leprosy’s prevalence has dropped significantly due to the effectiveness of MDT. In 2000, the World Health Organization declared it “eliminated as a public health problem” (<1 case per 10,000 people). Yet, these figures don’t tell the whole story. In 2023 alone, more than 200,000 new cases were reported across more than 120 countries, with the highest numbers in India, Brazil and Indonesia. In the United States, an average of about 176 cases were reported annually from 2014 to 2023, with a spike of 225 in 2023. Roughly one-third of U.S. cases from 2015 to 2020 were locally acquired, concentrated mainly in Florida and other coastal states.
Hansen’s disease is underreported, especially in rural or under-resourced areas where stigma and poor surveillance suppress diagnoses. Even when cases are detected, it often is too late to prevent serious harm. An estimated 3 to 4 million people currently live with visible impairments caused by untreated Hansen’s disease. Many delay seeking care due to fear, as leprosy still connotes curse and exile. In some countries, discriminatory laws continue to restrict the rights of cured individuals to obtain employment, hold public office or access public services.
This reality highlights why Hansen’s disease is classified as a neglected tropical disease (NTD). Alongside M. leprae’s preference for warm, humid climates, NTDs disproportionately affect the world’s poorest and most marginalized populations – those with the least access to healthcare, sanitation and health education. The burden of Hansen’s disease also reflects the concept of “Blue Marble Health,” which recognizes that diseases of poverty exist not only in low-income nations but also in underserved communities within wealthier ones.
So why does it persist if it’s curable? One major reason is case detection. In many endemic areas, healthcare workers are not adequately trained to recognize early signs and surveillance systems often don’t actively track the disease. Subsequent silent spread delays diagnosis until the damage is irreversible. School-based screenings, household contact evaluations and expanded rural outreach could make a meaningful difference, but all depend on sustained investment.
One of the most promising interventions for stopping transmission — one that also aligns with the United Nations Sustainable Development Goal 3, which promotes good health and well-being for all — is post-exposure prophylaxis (PEP). In this strategy, close contacts of those diagnosed with leprosy are given a single dose of rifampicin, which can cut their risk of developing the disease by up to 60%. This approach is cost-effective and straightforward, but it relies on effective contact tracing, a stable drug supply and a high level of trust. In places where stigma is high or people fear discrimination, contact tracing is less likely to be accepted. Even the best medical interventions fall short without community engagement and public education.
Community-driven programs are advancing efforts to eliminate Hansen’s disease. In India, which reports the highest number of cases globally, the government launched the Sparsh Leprosy Awareness Campaign (SLAC) in 2017 to promote early detection and public understanding. SLAC utilizes Gram Sabhas (village assemblies) and storytelling tools, such as “Sapna,” a school-aged girl mascot that helps humanize the message. Brazil’s Janeiro Roxo (“Purple January”) campaign lights clinics purple and sends trained health agents, often people who’ve recovered from Hansen’s disease, door-to-door for screening and awareness. In Indonesia, the National Action Plan for Leprosy (2023–2027) relies on kader (community health workers), religious leaders and survivors to identify cases and challenge stigma.
The WHO’s “Towards Zero Leprosy” roadmap outlines prevention goals by 2030, including the broader use of PEP and the repeal of discriminatory laws. A key prevention method is the BCG vaccine, used primarily for tuberculosis, which provides partial protection against Hansen’s disease: about 26% efficacy in controlled trials and around 60% effectiveness in real-world observational studies. A newer subunit vaccine candidate, LepVax, has shown safety and immunogenicity in Phase I trials in healthy adults and is now entering Phase Ib/IIa efficacy trials in Brazil.
Every year, thousands of people with Hansen’s disease are left undiagnosed. They live with preventable disabilities and endure isolation because a curable disease still carries an ancient stigma. We’ve had the tools to cure Hansen’s disease for decades. The question is whether we’ll use them to reach people who, like those my mother once saw behind glass, are still waiting to be seen.
By Shajee Khan
