Is Leprosy (Hansen's Disease) Contagious?

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Leprosy Risk Factors

People at highest risk are those who live in the areas where leprosy is endemic (parts of India, China, Japan, Nepal, Egypt, and other areas) and especially those people in constant physical contact with infected people. In addition, there is some evidence that genetic defects in the immune system may cause certain people to be more likely to become infected (region q25 on chromosome 6).

What is leprosy?

Leprosy, also termed Hansen's disease, is a chronic infection caused by the bacterium Mycobacterium leprae, a rod-shaped organism that stains reddish when an acid-fast stain is applied. Historians suggest leprosy was recognized as a disease as early as 600 BC; because of the disfigurement of individuals with untreated leprosy, people with leprosy have been shunned and isolated for many centuries. Fortunately, current multidrug therapy (MDT) has reduced leprosy so effectively that only a few countries still have individuals with this disease. Currently, the disease is rarely seen in the United States.

Leprosy has been classified into two major types: tuberculoid and lepromatous. However, there are intermediate subtypes (borderline, mid-borderline, and others). Tuberculoid leprosy has a more limited disease pattern and relatively few bacteria located in the infected tissue, while patients with lepromatous leprosy have widespread disease and much larger numbers of bacteria in infected tissue. These terms are still seen in the literature but are being replaced by the terms paucibacillary (for tuberculoid) and multibacillary (for lepromatous) types.

Mycobacterium leprae can infect armadillos that are indigenous to the southwest United States; occasionally, people can get leprosy if they handle these animals. Another form of leprosy is seen in dogs and cats (canine leprosy). Although canine leprosy is caused by Mycobacterium species, there is no good evidence that canine leprosy is transmitted to humans by pets.

Is leprosy contagious?

Leprosy is contagious but is considered to be only mildly contagious. However, acquisition of the disease usually occurs after long-term (months to years) contact with an untreated individual with the disease. It is passed from person to person via droplets from the nose and mouth during close and frequent contact with an untreated individual with leprosy.

Medically Reviewed by a Doctor on 10/10/2016

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