Leprosy Transmission

Although the bacteria responsible for the disease was discovered in 1873, scientists still do not fully understand the exact mode of leprosy transmission. Inhaled respiratory droplets are a likely source of infection. However, this is only a factor in half of all cases. Other things that may influence leprosy transmission include a person's degree of susceptibility, the extent of exposure, and environmental conditions.

Leprosy Transmission: An Overview

Despite first discovering Mycobacterium leprae (the bacteria that causes leprosy) in 1873, leprosy research scientists still do not completely understand the mode of leprosy transmission.
Most scientists believe that leprosy transmission occurs from person to person through infected respiratory droplets. While this may be one way in which the disease is spread, more than half of the people who develop it have no confirmed contact with an infected person. Factors that may influence leprosy transmission include:
  • The degree of susceptibility of the person
  • The extent of exposure
  • Environmental conditions.

Leprosy Transmission to Household Contacts

People who live in the same household as a person with untreated leprosy have an eight-fold increased risk of developing the disease. This is due to genetic factors relating to susceptibility and/or prolonged intimate contact. It is important to note that the spouse is the least at-risk familial member. The people who are at the greatest risk of leprosy transmission are:
  • Children
  • Brothers or sisters
  • Parents of someone with leprosy.


Leprosy transmission does not occur between a mother and her unborn baby, and people cannot get leprosy through sexual contact.

Other Modes of Leprosy Transmission

Although feral armadillos and nonhuman primates are known to carry Mycobacterium leprae, leprosy transmission from animals to humans has only been confirmed in a couple of cases and otherwise is extremely rare.

About Leprosy

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