Diseases Home > How Is Leprosy Spread?

Given the folklore that still surrounds the disease, many people wonder, "How is leprosy spread?" While infected respiratory droplets may be one way in which the disease is transmitted, over 50 percent of people who develop leprosy have no confirmed contact with an infected person. Scientists are still trying to determine how leprosy is spread and are now looking at genetic factors relating to susceptibility.

How Is Leprosy Spread? -- An Overview

Despite first discovering Mycobacterium leprae (the bacteria that causes leprosy) in 1873, leprosy research scientists still do not completely understand how leprosy is spread.
Most scientists believe that leprosy can be spread from person to person in infected respiratory droplets. While this may be one way in which leprosy is spread, more than 50 percent of the people who develop leprosy have no confirmed contact with an infected person. Factors that may influence how leprosy is spread include:
  • Environmental conditions
  • The degree of susceptibility of the person
  • The extent of exposure.

How Is Leprosy Spread to Household Contacts?

People who live within 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 family member. The people who are at the greatest risk of leprosy transmission are:
  • Parents of someone with leprosy
  • Children of someone with leprosy
  • Brothers or sisters of someone with leprosy.

Other Possible Modes of How Leprosy Is Spread

Leprosy cannot be spread from a mother to her unborn baby, and people cannot get leprosy through sexual contact.
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 leprosy cases.
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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