How Leprosy Spreads

The bacteria that causes leprosy (Mycobacterium leprae) was discovered in 1873; however, scientists still do not completely understand how leprosy spreads. Factors that may influence this include environmental conditions, a person's degree of susceptibility, and the extent of exposure. Although exactly how leprosy spreads is still being studied, it is known that the disease cannot be transmitted from a mother to her unborn baby or through sexual contact.

Leprosy Facts

How Leprosy Spreads: An Overview

Despite first discovering Mycobacterium leprae (the bacteria that causes leprosy) in 1873, leprosy research scientists still do not completely understand how leprosy spreads.

Most scientists believe that the disease is transmitted from person to person in infected respiratory droplets. While this may be one way in which the disease spreads, more than half of the people who develop leprosy have no confirmed contact with an infected person. Factors that may influence how leprosy spreads include:

The degree of susceptibility of the person
Environmental conditions
The extent of exposure.

How Leprosy Spreads to Household Contacts

People who live within the same household as a person with untreated leprosy have an eight-fold increased risk of developing leprosy. 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:

Parents of someone with leprosy
Children of someone with leprosy
Brothers or sisters of someone with leprosy.

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