Transmission of leprosy
Leprosy is known to occur at all ages ranging from early infancy to very old age. The youngest age reported for occurrence of leprosy is three weeks in Martinique (Montestruc & Berdonneau, 1954). The youngest case seen by the author was in an infant of two-and-a-half months, where the diagnosis of leprosy was confirmed by histopathology. Occurrence of leprosy, presumably for the first time, is not uncommon even after the age of seventy.
Method of transmission of leprosy
The exact mechanism of transmission of leprosy is not known. At least until recently, the most widely held belief was that the disease was transmitted by contact between cases of leprosy and healthy persons. More recently the possibility of transmission by the respiratory route is gaining ground. There are also other possibilities such as transmission through insects which cannot be completely ruled out.
Although leprosy affects both sexes, in most parts of the world males are affected more frequently than females often in the ratio of 2:1. This preponderance of males is observed in as diverse geographic situations as India, the Philippines, Hawaii, Venezuela and Cameroon. Doull et al (1942) from their studies in the Philippines have also pointed out that the difference as a true difference due to higher incidence among males, and not due to differing duration of disease for the two sexes. It it were the latter case, the sex-specific prevalence could be different even with the same sex-specific incidence. It should be pointed out that the male preponderance in leprosy is not universal and there are several areas, particularly in Africa, where there is either equal occurrence of leprosy in the two sexes, or occasionally even a higher prevalence among females. Such situations have been observed in Uganda, Nigeria, Malawi, Gambia, Burkina Faso, Zambia, Thailand and Japan.