The progression of leprosy includes skin ulcers and lesions accompanied by loss of sensation and eventual loss of digits and other extremities.

• Leprosy is a slowly developing, progressive disease that damages the skin and nervous system.
• An infection with Mycobacterium leprae or M. lepromatosis bacteria causes leprosy.
• Early symptoms begin in cooler areas of the body and include loss of sensation.
• Signs of leprosy are painless ulcers, skin lesions of hypopigmented macules (flat, pale areas of skin), and eye damage (dryness, reduced blinking). Later, large ulcerations, loss of digits, skin nodules, and facial disfigurement may develop.
• The infection spreads from person to person by nasal secretions or droplets. Leprosy rarely spreads from chimpanzees, mangabey monkeys, and nine-banded armadillos to humans by droplets or direct contact.
• Susceptibility to getting leprosy may be due to certain human genes.
• Antibiotics treat leprosy.

Leprosy is a disease mainly caused by the bacteria Mycobacterium leprae, which causes damage to the skin and the peripheral nervous system. The disease develops slowly (from six months to 40 years) and results in skin lesions and deformities, most often affecting the cooler places on the body (for example, eyes, nose, earlobes, hands, feet, and testicles). The skin lesions and deformities can be very disfiguring and are the reason that historically people considered infected individuals outcasts in many cultures. Although human-to-human transmission is the primary source of infection, three other species can carry and (rarely) transfer M. leprae to humans: chimpanzees, mangabey monkeys, and nine-banded armadillos. The disease is termed a chronic granulomatous disease, similar to tuberculosis, because it produces inflammatory nodules (granulomas) in the skin and peripheral nerves over time.

Is Leprosy Contagious?

Leprosy is contagious but is considered to be only mildly contagious. However, acquisition of the disease usually occurs after long-term (months to years) contact with an untreated individual with the disease. It is passed from person to person via droplets from the nose and mouth during close and frequent contact with an untreated individual with leprosy.

Since the disease often appeared in family members, some people thought it was hereditary. Other people noted that if there was little or no contact with infected individuals, the disease did not infect others. Consequently, some cultures considered infected people (and occasionally their close relatives) as "unclean" or as "lepers" and ruled they could not associate with uninfected people. Often infected people had to wear special clothing and ring bells so uninfected people could avoid them.

The Romans and the Crusaders brought the disease to Europe, and the Europeans brought it to the Americas. In 1873, Dr. Hansen discovered bacteria in leprosy lesions, suggesting leprosy was an infectious disease, not a hereditary disease or a punishment from the gods. However, many societies still ostracized patients with the disease, and religious personnel at missions cared for those with leprosy. Patients with leprosy were encouraged or forced to live in seclusion up to the 1940s, even in the United States (for example, the leper colony on Molokai, Hawaii, that was established by a priest, Father Damien and another colony or leprosarium established at Carville, La.), often because no effective treatments were available to patients at that time.

Because of Hansen's discovery of M. leprae, researchers made efforts to find treatments (anti-leprosy agents) that would stop or eliminate M. leprae. In the early 1900s to about 1940, medical professionals injected oil from Chaulmoogra nuts into patients' skin was with questionable efficacy. At Carville in 1941, promin, a sulfone drug, showed efficacy but required many painful injections. Dapsone pills were found to be effective in the 1950s, but soon (1960s-1970s), M. leprae developed resistance to dapsone. Fortunately, drug trials on the island of Malta in the 1970s showed that a three-drug combination (dapsone, rifampicin [Rifadin], and clofazimine [Lamprene]) was very effective in killing M. leprae. The World Health Organization (WHO) recommended this multi-drug treatment (MDT) in 1981 and remains, with minor changes, the therapy of choice. MDT, however, does not alter the damage done to an individual by M. leprae before starting MDT.

Currently, there are several areas (India, East Timor) of the world where the WHO and other agencies (for example, the Leprosy Mission) are working to decrease the number of clinical leprosy cases and other diseases such as rabies and schistosomiasis that occur in remote regions. Although health researchers hope to eliminate leprosy like smallpox, endemic (meaning prevalent or embedded in a region) leprosy makes complete eradication unlikely. In the U.S., leprosy has occurred infrequently but is endemic in Texas, Louisiana, Hawaii, and the U.S. Virgin Islands by some investigators.

Leprosy is often termed "Hansen's disease" by many clinicians in an attempt to have leprosy patients forgo the stigmas attached to a leprosy diagnosis.