Leprosy (Hansen's Disease)

Leprosy (Hansen's Disease) is a chronic infectious disease that primarily affects the peripheral nerves, skin, upper respiratory tract, eyes, and nasal mucosa (lining of the nose). The disease is caused by a bacillus (rod-shaped) bacterium known as Mycobacterium leprae.

Why Is the Study of Leprosy (Hansen's Disease) a Priority for NIAID?

At the beginning of 2010, the registered prevalence of leprosy in the world was 211,903 cases, and 244,796 new cases were detected during 2009, as reported by 141 countries (World Health Organization [WHO]). Since the 1980s, when the WHO initiated its Leprosy Elimination Project, more than 14 million cases have been cured. However, the number of new cases being detected annually is raising the unanswered questions about the infection source, transmission, and incubation period of leprosy.

How Is NIAID Addressing This Critical Topic?

Researchers are exploring more avenues than ever before in the search for solutions to leprosy, now that the genome of M. leprae has been sequenced. NIAID goals are to discover reservoirs of infection, routes of transmission, and incubation periods so the disease can be stopped before patients even have symptoms. New tests for early detection of leprosy before nerve damage occurs are now being developed.

Innovative research efforts are addressing such issues as transmission and the true extent of leprosy incidence. Studies are focusing on the areas of early detection (prior to developing clinical symptoms), prevention of nerve damage, surveillance of areas where drug resistance is occurring, and molecular epidemiology. 

To learn about risk factors for Leprosy and current prevention and treatment strategies visit the Centers for Diseases Control and Prevention (CDC) Leprosy site.

Micrograph of skin section from leprosy patient.
Credit: NIAID

Some classic histopathologic changes found in a skin section from a person with leprosy.

Basic Research

NIAID-funded investigators are developing the armadillo as a research animal model for human leprosy and developing improved skin test antigens to detect leprosy. 


NIAID-funded scientists are using genomic knowledge of M. leprae to examine leprosy transmission. From earlier epidemiological studies, scientists knew that M. leprae had been found among wild armadillos in Texas and Louisiana, suggesting that human contact with infected armadillos might lead to infection.

Next Steps for Leprosy Research

Priorities for research in leprosy today include genetic probes for molecular epidemiology, and new immunologic tests for early detection of leprosy before nerve damage occurs. The goals are to provide evidence on routes of transmission and incubation periods and to develop new tools to prevent and, ultimately, eradicate leprosy.