Hansen's disease, also known as leprosy, is an infectious disease caused by infection by Mycobacterium leprae. The modern name of the disease comes from the discoverer of Mycobacterium leprae, G. A. Hansen. Sufferers from Hansen's disease have generally been called lepers, although this term is falling into disuse both from the diminishing number of leprosy patients and from pressure to avoid the demeaning connotations of the term.
Leprosy used to be incurable and severely disfiguring. Lepers were shunned and sequestered in leper colonies. Today, leprosy is easily curable by multidrug antibiotic therapy. The main challenges for Hansen's disease elimination efforts are to reach populations that have not yet received multidrug therapy services, improve detection of the disease, and provide patients with high-quality services and affordable drugs.
Other than humans, the only other animal known to be susceptible to leprosy is the armadillo.
Hansen's disease has been recognized as a problem since the beginning of recorded history. Lepers have frequently lived on the edge of society, and the disease was often believed to have been caused by a divine (or demonic) curse or punishment.
The Bible contains many references to "leprosy", which do not necessarily concern Hansen's disease. These words seem to have been used to cover a number of skin conditions of different etiology and severity. Under ancient Israelite law, the priests were required to be able to diagnose leprosy. The Israelites also used quarantine to prevent its spread.
Minorities like the Navarrese agotes were accused of being lepers.
The disease is caused by a bacillus which multiplies very slowly and mainly affects the skin, nerves, and mucous membranes. The organism has never been grown in bacteriologic media or cell culture, but has been grown in mouse foot pads. It is related to M. tuberculosis, the bacillus that causes tuberculosis.
The mode of transmission of Hansen's disease remains uncertain. Most investigators think that M. leprae is usually spread from person to person in respiratory droplets. What is known is that the transmission rate is very low.
This chronic infectious disease usually affects the skin and peripheral nerves but has a wide range of possible clinical manifestations. Patients are classified as having paucibacillary or multibacillary Hansen's disease. Paucibacillary Hansen's disease is milder and characterized by one or more hypopigmented skin macules. Multibacillary Hansen's disease is associated with symmetric skin lesions, nodules, plaques, thickened dermis, and frequent involvement of the nasal mucosa resulting in nasal congestion and epistaxis (nose bleeds).
In 1999, the world incidence of Hansen's disease was estimated to be 640,000; and in 2000, 738,284 cases were identified. In 1999, 108 cases occurred in the United States. In 2000, the World Health Organization (WHO) listed 91 countries in which Hansen's disease is endemic, with India, Myanmar, and Nepal having 70% of cases. In 2002, 763,917 new cases were detected worldwide, and in that year the WHO listed Brazil, Madagascar, Mozambique, Tanzania and Nepal as having 90% of Hansen's disease cases.
Worldwide, 1-2 million persons are permanently disabled because of Hansen's disease. However, persons receiving antibiotic treatment or having completed treatment are considered free of active infection.
Hansen's disease is one of the infectious diseases tracked passively by the Centers for Disease Control and Prevention. Its prevalence in the United States has remained low and relatively stable. There are decreasing numbers of cases worldwide, though pockets of high prevalence continue in certain areas such as the western Pacific.
Those having close contacts with patients with untreated, active, predominantly multibacillary disease, and persons living in countries with highly endemic disease are at risk for contracting the disease. Recent research suggests that there is genetic variation in susceptibility. The region of DNA responsible for this variability is also involved in Parkinson's disease, giving rise to current speculation that the two disorders may be linked in some way at the biochemical level.
There are still a few "leper colonies" around the world, in countries such as India and the Philippines. In the United States, the tiny island of Molokai in the Hawaiian chain contains that country's oldest asylum.
In 2001, government-run leper colonies in Japan came under judicial scrutiny, leading to the determination that the Japanese government had mistreated the patients (http://news.bbc.co.uk/1/hi/world/asia-pacific/1350630.stm).