Epidemiology of leprosy. Molecular, biological, and immunological approach.

Leprosy is an infectious disease for which humans are considered the only source of infection. The major hindrance in leprosy control and thus in reaching the elimination goal is that numerous leprosy cases remain undetected for a long time. Many of these patients are a continuous source of infection and, and hence perpetuate transmission. The goal of the World Health Organization (WHO) is to eliminate leprosy as a public problem by the year 2000; that is, to reach as a global prevalence of <1 per 10,000 people. The epidemiological data generated routinely by health services are greatly influenced by their policies and activities. The data do not, however necessarily reflect the true situation in the field. Information on the magnitude of the leprosy problem in any one area is important for the health services with regard to their planning, monitoring and evaluation of leprosy control activities. Our studies have suggested that the high prevalence of antibodies in children may be indicative of the active transmission of M. leprae in their surroundings. The prevalence of these antibodies may also be important for leprosy control programs in order to detect new patients as early as possible and in an effective and sustainable manner. Based on PCR data, it seems that the environment also plays an important role in the transmission of leprosy in endemic areas. The results of our study show that contact with a leprosy patient is the major determinant in the incidence of leprosy and that this concept shows similarities with the "stone-in-the-pond" principle of tuberculosis transmission in concentric circle around patients.