Hansen’s disease, or leprosy, in Florida: What to know

Hansen’s disease is caused by bacteria called Mycobacterium leprae or Mycobacterium lepromatosis. It typically causes various skin abnormalities and can damage the peripheral nervous system. Not everyone who is infected will develop the clinical disease that results from chronic infection. For those who do, it can take years after initial exposure for signs and symptoms to appear since the bacteria are slow-growing. There are various manifestations of Hansen’s disease, including tuberculoid, borderline tuberculoid, borderline lepromatous and lepromatous leprosy. Precisely which manifestation a person develops depends on the type of immune response their body mounts against the bacteria.

Hansen’s disease basics

Hansen’s disease is one of the oldest infectious diseases documented in the historical record, described in the literature of ancient civilizations. Commonly known as leprosy, its more recent namesake is the Norwegian physician who discovered the bacterium M. leprae in 1873, Gerhard Henrik Armauer Hansen. He identified the bacterium as the cause of leprosy, disproving theories of heredity and helping reduce the centuries-old social stigma associated with the disease. The National Hansen’s Disease Program reported 205 new cases in 2024, with Florida being one of the top reporting states.  

The infection is caused by M. leprae and, rarely, by M. lepromatosis. In the U.S., locally acquired case numbers of Hansen’s disease typically correlate with the natural habitat range of the nine-banded armadillo, a reservoir host of the bacteria. The most obvious symptoms of Hansen’s disease are skin lesions. Manifestations include, but are not limited to, thickened skin, nodules and reddish or light lesions. 

Because Hansen’s disease also attacks the nerves outside the brain and spinal cord, or the peripheral nerves, there can be a loss of sensation, beginning with tingling before progressing to numbness and painlessness. The affected nerves also become enlarged and palpable. 

Hansen’s disease in Florida

Florida has one of the highest known rates of locally acquired Hansen’s disease infection in the country. The nine-banded armadillo is a natural reservoir for M. leprae, which lives throughout the Sunshine State. Case numbers correlate with the natural range of the nine-banded armadillo, but more research is needed to better understand how it’s transmitted and who is at risk for the disease in Florida.  

Hansen’s disease is a rare infectious disease, but awareness in Florida is important. There has been an uptick in locally acquired cases of Hansen’s disease in north and central Florida over the last five to ten years. While Hansen’s disease is treatable and curable, the longer you experience symptoms, the more likely you are to develop chronic issues. Early recognition is key; if you have concerns about Hansen’s disease, speak with your healthcare provider.  

Hansen’s disease transmission

The complex transmission cycle of the disease is still being investigated. Transmission from the nine-banded armadillo to humans has been reported, likely when the two come into direct or indirect contact. Those with multibacillary Hansen’s disease, or lepromatous leprosy, are believed to have high numbers of bacteria in their respiratory droplets and nasal secretions. Human-to-human spread can occur through prolonged close contact.  

There have been cases of infection without direct contact with an infected person or an armadillo. One hypothesis is that those handling soil contaminated by an armadillo may be at risk of transmission. The nine-banded armadillo often looks for insects to eat by digging in foliage and flowerbeds, then rests in a burrow that can be close to human dwellings. Humans should avoid directly touching the soil of an armadillo burrow, as there have been cases of Hansen’s disease described in those who have had only this type of exposure. Researchers at the University of Florida Emerging Pathogens Institute are investigating these potential risk factors to better understand these hypotheses.  

Symptoms of Hansen’s disease

The bacteria that cause Hansen’s disease grow very slowly. It may take up to 20 years after exposure to the bacteria for signs of the disease to develop. Symptoms mainly affect the skin, nerves and lining of the nose. If left untreated or treated late, it can cause serious complications and disabilities. 

Populations most vulnerable to Hansen’s disease infections

Only approximately 5% of the human population is at risk for Hansen’s disease infection due to natural immunity against M. leprae. Those living in areas where it is common are at higher risk of infection, including parts of Asia, Africa and South America. Those who spend prolonged periods of time with those suffering from a chronic infection are also at higher risk of infection. 

Hansen’s disease diagnosis

Healthcare providers can diagnose Hansen’s disease by conducting an exam and running diagnostic tests, such as skin biopsies. They may look for patches of skin that appear lighter, darker, or redder than the person’s normal skin and determine whether those patches have a loss of feeling.

To confirm the diagnosis, healthcare providers will take a skin or nerve sample for microscopic examination to detect the bacteria that cause Hansen’s disease. They may also do tests to rule out other skin diseases. 

The disease commonly manifests as skin lesions and peripheral nerve involvement. Leprosy is diagnosed by finding at least one of the following cardinal signs: (i) definite loss of sensation in a pale or reddish skin patch; (ii) thickened or enlarged peripheral nerve, with loss of sensation and/or weakness of the muscles supplied by that nerve; (iii) microscopic detection of bacilli in a slit-skin smear. 

Based on the above, cases of Hansen’s disease are classified into two types for treatment purposes: a paucibacillary case and a multibacillary case. 

• PB case: a case of Hansen’s disease with one to five skin lesions, without demonstrated presence of bacilli in a skin smear. 
• MB case: a case of Hansen’s disease with more than five skin lesions, with nerve involvement or with the demonstrated presence of bacilli in a slit-skin smear, irrespective of the number of skin lesions. 

Hansen’s disease treatment

There are several medications that target the bacteria that we can use. It can be a combination of several antibiotics that will need to be taken for several months or up to two years. While Hansen’s disease is treatable and curable, the longer one experiences symptoms, the more likely one is to develop chronic issues. 

Hansen’s disease prevention

Given the correlation between case numbers and the nine-banded armadillo population, avoiding close contact with the animal is the best way to prevent direct infection. It is also important to try and keep armadillos away from your home. Working with wildlife management services is an assured way to remove unwanted animal visitors. It’s also possible for transmission to occur through contact with soil contaminated with the Hansen’s disease bacteria. This has not been confirmed at this time, but to be safe, people who garden, work in agriculture, landscaping or otherwise have close contact with soil should protect their hands and extremities with gloves and clothing that would prevent contamination. Cover any open cuts or scratches to prevent soil contamination and bacterial infection. Research suggests that M. leprae may survive temporarily in soil. Wearing gloves while working with soil is a simple precaution that helps protect against cuts and getting soil into wounds. 

If caring for someone with a chronic Hansen’s disease infection, be sure to wear appropriate personal protective equipment, such as gloves and a mask. Respiratory droplets have been observed to transmit the bacteria in past cases. Although treatable and rare, vigilance is the best way to prevent Hansen’s disease infection.  

Additional resources