What causes leprosy

Leprosy is caused by a bacterium called Mycobacterium leprae. It multiplies extremely slowly — dividing roughly once every two weeks, against once every twenty minutes for common bacteria. That single fact explains almost everything strange about the disease.

Because the bacteria are so slow, symptoms can take three to five years to appear, sometimes twenty. A person can carry the infection through an entire decade of ordinary life before the first patch shows. And because the bacteria prefer the cooler parts of the body, they settle in the nerves closest to the skin — the hands, feet, face and ears.

The first sign, and how to check for it

The earliest sign is a patch of skin that has lost sensation. It may be paler than the skin around it, or slightly reddish. It is usually flat, dry, and does not itch.

Other early signs worth acting on:

• Numbness or tingling in the hands or feet, especially if it does not go away.
• Weakness — dropping things, sandals slipping off, difficulty holding a pen.
• A painless wound on the sole of the foot that keeps returning.
• Loss of eyebrow hair at the outer edge, or thickened earlobes.
• A nerve you can feel as a thick cord near the elbow or behind the knee.

How leprosy spreads — and how little it spreads

Transmission is through droplets from the nose and mouth of an untreated patient, over months or years of close, repeated household contact. It is not spread by shaking hands, sharing food, sitting together, or by touch of any kind.

Around 95 out of 100 people have natural immunity and cannot develop the disease even with heavy exposure. And a patient stops being infectious within days of the first dose of treatment. The person you are afraid to sit beside is, in almost every case, already not infectious.

It is not hereditary. It is not a punishment. It is not a curse. It is a bacterium.

The cure: multi-drug therapy

Since 1982, leprosy has been cured with multi-drug therapy — a combination of rifampicin, clofazimine and dapsone. In India, MDT is supplied free of cost at every government primary health centre under the National Leprosy Eradication Programme.

• Paucibacillary leprosy (few bacteria, usually one to five patches): six months of treatment.
• Multibacillary leprosy (more widespread): twelve months of treatment.

Completion rates are the problem, not availability. People stop when the patch fades, because they feel cured. The bacteria are not gone at that point, and stopping is how relapse and resistance begin.

Why people still lose fingers, if it is curable

This is the part almost nobody understands, so read it carefully. Leprosy does not eat flesh. It destroys the nerves that carry sensation.

A person with damaged nerves picks up a hot vessel and does not feel it burn. Walks a kilometre on a stone in the sandal and does not feel it cut. The injury goes unnoticed, gets infected, the infection reaches the bone, and tissue is surgically lost. Every step of that chain is preventable — with protective MCR footwear, a daily habit of inspecting the hands and feet by eye rather than by feel, and wound care the moment something opens.

That is why our field workers spend as much time on footwear and dressing kits as on medicine. The medicine cures the disease. The footwear saves the foot.

What happens after diagnosis in India

Medically, the path is clear and free. Socially, it is not. We routinely meet people who have been asked to leave a rented room, refused service at a shop, removed from a family gathering, or quietly divorced. A number of Indian laws still permit leprosy as a ground for divorce or disqualification, though several have been repealed in recent years.

The result is that people hide the patch. They hide it until the numbness spreads, and by the time they reach a clinic the nerve damage is permanent. Roughly one in twenty new patients in India already has visible disability at diagnosis — a number that means the system found them years late.

Stigma is not a side issue in leprosy. Stigma is the mechanism by which a curable disease becomes a permanent disability.

What we do about it

We run detection camps in the colonies and villages nobody visits, supply MDT support and dressings, distribute MCR footwear, fund reconstructive surgery for claw hand and foot drop, and pay school fees for the children of leprosy-affected families so the next generation walks in on equal footing.

See last year's work in numbers or look at the people currently waiting.