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Leprosy has been a dreaded scourge since biblical times. The chronic slow progression of the disease, its contagiousness, the associated disfigurement and disability, and, until recently, the absence of any recognised cure, meant the exclusion and ostracism of the sufferers into isolated communities in the form of leprasoria. Marked social stigma is associated with the disease. Infection with Mycobacterium leprae is largely acquired through inhalation. Endonasal examination in established cases of leprosy often shows unsuspected lesions of the mucosa. Nasal secretions of patients as well as droplets during sneezing are major sources of transmission. As many as 108 bacilli may be shed in 24 hours in nasal secretions. Ulceralive lesions of the skin of patients are another source of shedding of bacteria. The survival of M. leprae outside the human body can vary from 7 to 60 days depending upon the environmental temperature and humidity. nside the body M. leprae multiplies slowly, hence the long incubation period. Many close contacts of patients with no symptoms or clinical lesions may harbour the bacilli in their skin. Biopsies of skin from unselected sites in family contacts of established cases of leprosy show the presence of acid fast bacilli. Whether they can also transmit the disease and thus are acting as symptomless carriers in the community is not known. The risk of acquiring infection varies among individuals. In endemic areas, M. leprae is transmitted easily, but 95 per cent of the people who are infected never acquire the disease. Moreover, in early infection, regression and spontaneous healing are known to occur.
Michel L. Garenne (Mon,) studied this question.