Britannica Sources used in this answer

Why is prolonged close contact important in the transmission of leprosy?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Sign reading Gandhiji Prem Nivas Leprosy Centre Titagarh conducted by Missionaries of Charity, with a crucifix above the sign on a decorated building facade. — leprosy The Gandhiji Prem Nivas is a center for people with leprosy that was established by Mother Teresa in 1958 and is run by the Missionaries of Charity in Titagarh, India.

While it is often stated that leprosy is transmitted through prolonged close contact, it is important to clarify that the exact mechanism of transmission remains a subject of scientific uncertainty.1

The emphasis on prolonged close contact stems from the observation that the infection is remarkably difficult to contract. Approximately 95 percent of the population is not susceptible to Mycobacterium leprae, the bacterium responsible for the disease, and will not develop it even after repeated exposure.1

Research indicates that the bacillus can enter the body through the mucous membranes of the nose or through breaks in the skin. Because the infection is not easily transmitted, the requirement for prolonged, intimate interaction likely reflects the low probability of the pathogen successfully establishing an infection in a susceptible host. Furthermore, the disease is characterized by a very long incubation period—typically three to five years—which complicates efforts to pinpoint specific transmission events.123