Leprosy (Hansen's disease): Technical Information
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Clinical Features
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.
Etiologic Agent
Mycobacterium leprae, a bacillus that multiplies very slowly and mainly affects the skin, nerves, and mucous membranes, is the organism responsible for Hansen’s disease. The organism has never been grown in bacteriologic media or cell culture, but has been grown in mouse foot pads.
Incidence
In 2008, the number of new cases detected worldwide was 249,007. In 2007, 109 cases occurring in the United States were reported to CDC. In 2008, Brazil, India, and Indonesia had 77% of all cases reported to the World Health Organization (WHO). Over 94% of all reported cases are reported from 17 countries.
Sequelae
Worldwide, 1-2 million persons are permanently disabled as a result of Hansen's disease. However, persons receiving antibiotic treatment or having completed treatment are considered free of active infection.
Transmission
Although 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.
Risk Groups
Close contacts of patients with untreated, active, predominantly multibacillary disease, and persons living in countries with highly endemic disease are at risk of contracting Hansen’s disease.
Surveillance
Hansen's disease is nationally notifiable in the United States.
Trends
Prevalence has remained relatively stable in the United States. Cases appear to be predominantly related to immigration. Worldwide, the number of cases are decreasing, however, there are pockets of high prevalence in certain countries.
Challenges
Multi-drug therapy has not been implemented in many endemic areas. Early case finding is difficult in many areas where the disease is most prevalent. Nerve damage must be recognized and managed. Relapse rate after completion of short course multi-drug therapy may rise.
Opportunities
Opportunities exist for participation in Hansen's disease elimination activities in endemic-disease countries, and for Mycobacterium research in the Laboratory Research Branch of the National Hansen's Disease Program.
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