Mycobacterium leprae: Common ways through which leprosy is spread

Mycobacterium leprae is the bacteria that causes leprosy.

Leprosy is not a very infectious disease – in other words, it is not highly infectious (it is mildly infectious). It does not spread from person to person very easily.

Not everyone that is exposed to Mycobacterium leprae develops leprosy. According to research, only a few people (about 5-10% of the population) have been found to be susceptible to the disease due to immunological factors.

  • Transmission usually occurs when the infected person coughs or sneezes. This releases droplets containing the leprosy bacteria into the air. The droplets or secretions are said to come in contact inner lining of the nostrils, from where the infection proceeds.

It is very important to know that an individual who has leprosy can spread it only when he/she has not been treated with the anti-leprosy drugs.

Shortly after an infected person starts treatment, he/she stops being infectious (that is, he/she can no longer spread the leprosy bacteria).

  • Leprosy is transmitted though frequent, repeated and close contact with droplets from the nose and/or mouth, or nasal secretions (nasal fluid) of an infected person who has not been treated. An individual has to be in contact with a person with untreated leprosy for a long period of time (months to years) to become infected with leprosy.
  • It has also been said that infection can also be initiated when the droplets containing the leprosy bacteria come in contact with broken skin. In other words, the Mycobacterium leprae (the leprosy-causing bacteria) cannot infect skin that is intact.
  • The disease is mainly transmitted from human to human.
  • However, it can also be carried by three other animals – Mangabey monkeys, nine-banded armadillos and chimpazees. These animals can transmit leprosy to humans.
  • Some people have probably heard that cockroaches cause leprosy and wondered how true it is. Cockroaches can act as vectors, carrying the leprosy bacteria; and so they can transmit leprosy.

Repeated, frequent and close contact with the leprosy-causing bacteria (Mycobacterium leprae) is the commonest way through which leprosy is spread.

Somso Kizor enjoys words. She loves reading good books and writing - amongst other things. Somso is passionate about educating people about their health; as this would reduce the burden of diseases and deaths (hence, suffering) all over the world. Let's not forget the popular saying that goes "health is wealth." For more details, send an email to


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