The Centers for Disease Control and Prevention published a research letter on Monday sounding the alarm about rising cases of leprosy in Florida.

After reviewing data from 2020, the most recent data on the condition available from the CDC, epidemiologists are concerned that the skin and neurological disease is becoming endemic, or native, to certain parts of Florida, possibly spreading across the Sunbelt.

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"Florida, USA, has witnessed an increased incidence of leprosy cases lacking traditional risk factors. Those trends, in addition to decreasing diagnoses in foreign-born persons, contribute to rising evidence that leprosy has become endemic in the southeastern United States," reads the letter published in the CDC's platform Emerging Infectious Diseases.

Here is what you need to know about the emerging public health threat.

What is happening in Florida?

The leprosy cases in central Florida account for one-fifth of the 159 new cases of the disease in the U.S. in 2020. In Florida, the cases in the central part of the state accounted for 81% of the total.

Although leprosy in the U.S. is exceedingly rare, the majority of cases are either acquired through foreign travel to areas where the disease is endemic or by contact with infected animals.

According to the research letter, however, approximately 34% of the Floridian leprosy cases were locally acquired, suggesting "mounting epidemiological evidence" that leprosy is becoming endemic, or native, to parts of Florida.

What is leprosy, and how is it spread?

The World Health Organization reports there are more than 200,000 cases of leprosy per year worldwide, and the number has gradually increased in the U.S. since the early 2000s.

Leprosy, known as Hansen's disease, typically manifests through painful skin lesions and peripheral nerve damage. If untreated, the disease can cause paralysis of the hands and feet, chronic nonhealing ulcers, blindness, and permanent nerve pain.

The disease is treatable with a three-drug antibiotic combination, killing the pathogen that causes the disease within six to 12 months, depending on the specific characteristics of the infection.

Although there may be zoonotic transmission from armadillos in certain parts of the South, the primary spread of leprosy is thought to be through respiratory droplets.

"The disease is not spread through casual contact with a person who has leprosy like shaking hands or hugging, sharing meals or sitting next to each other," the WHO said, adding that infected people stop transmitting the disease shortly after treatment.

What is the role of migration?

The authors of the research letter suggest that international migration may be a cause for the growing leprosy case counts in the U.S., which have grown in correlation with rising immigration rates.

"Reports from the [CDC] show that, although the incidence of leprosy has been increasing, the rates of new diagnoses in persons born outside of the United States has been declining since 2002," the authors wrote. "The number of international migrants in North America increased from 27.6 million persons in 1990 to 58.7 million in 2020, so a link to migration may account for the increase in incidence of leprosy in historically nonendemic areas."

Given that there is little evidence for animal-to-human spread in Florida, "there is some support for the theory that international migration of persons with leprosy is a potential source of [native] transmission."

What is the public health response?

The Florida Department of Health did not respond to the Washington Examiner's request for comment on the research letter or for the most recent numbers.

Medical practitioners must report leprosy within one business day to the Florida Department of Health to conduct contact tracing to contain the outbreak.

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"Contact tracing is critical to identifying sources and reducing transmission," the authors of the research letter wrote. "By increasing local physician efforts to report incidence and supporting further research to assess routes of transmission, a congruent effort can be made to identify and reduce spread of the disease."

"Case detection and treatment with ... alone have proven insufficient to interrupt transmission," the WHO said.