Twice Neglected: the disease characterized by its absence

“I can't bend my fingers anymore,” a woman says, working at her fists, trying to open them to demonstrate. She pushes a plastic chair across the bare floor in her modest living room and leans closer. "See? I never know when my hands will open or close." Overhead, the soft tick of the ceiling fan interrupts the droning heat in the room.

Dr. Lucia Fraga, an immunologist who has studied leprosy in Brazil for decades, takes her hand and turns it over. She runs a thin nylon wire along her forearm. The woman, whom we’ll call Celia, doesn’t flinch. She has not registered that anything has touched her at all.

Fraga runs a longitudinal cohort assessing leprosy onset in Governador Valadares (GV), Brazil. Her study serves a double purpose: it tracks risk in communities and catches the disease early, before referring people for treatment.

“In the case of a person with a family history of leprosy who lives in an endemic area but does not yet show suggestive clinical signs, I advise them to participate in the leprosy research project we are conducting,” explains Fraga. “This project covers medical consultation and laboratory tests.”

By the time Celia’s hand goes numb, the leprosy bacterium may have been at work for years. Her curling fingers are characteristic of the disease’s symptomology, and mark a record whose cardinal sign is absence: skin that stops feeling cold, or a foot that cannot sense stones in a shoe. Nerve damage, loss of sensation, and skin changes are few among the major physical manifestations of leprosy, with damage accruing silently over time. 

Leprosy, now commonly known as Hansen's disease, is a slow-moving bacterial infection that attacks the skin, the nerves, and the eyes. Three people could be exposed at the same time: one might develop the disease in five years, the second in twenty, the third never at all. Scientists still don't fully understand why. Alongside tuberculosis, its close bacterial cousin, leprosy is among the oldest infectious diseases known to medicine. 

Celia noticed the numbness, but brushed it off for months before finally being pushed to seek care, a delay that Dr. Fraga sees regularly among new patients.

“One of the main challenges in leprosy control is late diagnosis, which fosters the development of physical disabilities and psychosocial consequences stemming from the stigma associated with the disease,” Fraga explains. “Timely diagnosis, performed early, accelerates the initiation of multidrug therapy, reduces the risk of physical disabilities, and contributes to breaking the chain of disease transmission within the community”. 

In 2023, health systems worldwide reported 182,815 new cases of leprosy. About 14,908 of those were found through active case finding, through contact examination and screening campaigns. The remaining likely came the way she did: on their own, once the disease pushed them to go looking for care.

Most recently in 2025, 5.6 percent of new patients globally were diagnosed with grade 2 disability, the World Health Organization's (WHO) term for visible, irreversible damage. In Brazil, where Celia lives, the grade 2 disability rate is closer to one in ten, roughly twice the global rate. Nearly 8344 of the new global cases were among children, which means the bacterium is still moving through households in real time.

Leprosy has been formally classified as a neglected tropical disease—a global infectious disease classification describing a class of 21 infectious diseases that are globally and historically associated with socioeconomic challenges, poverty, and often permanent, compounding health outcomes. 

The nomenclature  “neglected” is descriptive of their absence from global research agendas, low R&D profitability, and limited funding. Leprosy’s disability rate points at a second, quieter neglect: not just how much the disease is researched, but also, how comprehensively ongoing cases are searched for. Brazil's detection is weakest in the municipalities where the disease carries highest disability rates, a pattern that makes the country's falling case counts genuinely ambiguous. 

Multidrug therapy has been free through WHO’s partnership with Novartis since the mid-1990s, but treatment only addresses the portion of the problem a clinic can see, which is the end of a process that began years earlier. In a handful of places, researchers have started at the other end: examining households around a known case, screening the neighborhoods where cases cluster, sampling local environments, and testing for antibodies that indicate infection before clinical signs appear. Each method catches a different kind of patient; Together, they each complete one part of the relay towards detection.

"I wish I didn't have to tell them to be careful about who they tell," says Jessica Fairley, MD, MPH, an infectious disease physician at Emory University. Fairley runs one of the satellite clinics for the National Hansen’s Disease Program, as well as research projects in Ethiopia and in Brazil to assess novel infection onset patterns. "It's hard to say that leprosy is treatable and not really contagious in one breath and then turn around and say, well, but you really should keep it to yourself, because your neighbors may not understand". 

Fairley ‘s research centers on what makes people susceptible to the disease, as well as emerging exposures beyond just person-to-person contact. In Fairley's domestic clinical work, despite there being strong local referral systems and early detection, much of her visits involve navigating patient stigma, education, and reassurance.

Globally, patients still face discrimination written into law– grounds for divorce, bars to public office, employment restrictions– which pushes diagnosis later, and disability closer.

"While the rates of incidence have gone down, the percentage of people with disability at the time of diagnosis have stayed the same or gone up,” says Fairley. “If you're not even getting the people with visible disabilities, then you're for sure missing other people.”

The neglect compounds with time siphoning care. Experts are seeing that the system fails patients twice. First by missing their initial diagnosis, and later by abandoning them once they are officially 'cured.'  Even after the bacteria is gone, chronic immune reactions and nerve damage can persist for years without care. 

Cassandra White, a medical anthropologist at Georgia State University, is the author of An Uncertain Cure, a book about delayed diagnosis, stigma, and what living with leprosy actually involves. White adds another dimension to leprosy neglect: leprosy reactions, or long term chronic autoimmune reactions to the dead bacilli, sometimes mimicking the disease itself.

“For some people, [leprosy reactions can occur], in my experience talking to people, up to ten years, maybe even more after they're cured,” she says.

While global health agencies push for elimination, public health experts warn that standard definitions fail to capture the reality of leprosy. For an ancient disease deeply tied to social stigma and delayed diagnosis, how official targets define "elimination" dictates who receives care and who gets left behind.

Elimination, in public health, does not carry its colloquial meaning: the WHO’s target is one positive case per 10,000 people, not zero. Programs now also aim at zero leprosy, a phrase White finds slippery. "What does zero mean?” White says.  “Zero can mean different things. A different concept could be zero transmission, zero stigma, but zero numbers is almost impossible.”

Fraga describes an added challenge: misdiagnosis within health systems being driven by limited knowledge of how to diagnose leprosy across different skin colors, a likely result of racial and colorist influence in the region.

“[Ongoing research] notes significant concern among patients that physicians were unable to diagnose the disease with confidence or identify it within non-white communities—particularly among those with darker skin tones”, Fraga describes. 

What 'zero' means on paper matters very little to the woman sitting in the clinic. Even if official targets declare the disease eliminated, the mycobacterium has already left its mark on her nerves. According to Fairley, eliminating the disease requires addressing these patients still slipping through the cracks—particularly those delayed by diagnostic bias or historic burden of stigma. 

“There is a definite trend, across the world, where governments and districts don’t want to be associated with leprosy or Hansen's disease, you know. It's stigmatizing, [it is] a marker, in many places of poverty, so countries would be worried about their reputation as being a hotspot for leprosy. Not to say that places will cover up cases, but they might not look for them, and that might be a problem.”