Central Florida hotspot of rising leprosy cases in the US

Leprosy disease

Mycobacterium leprae bacteria cause leprosy. 

Leprosy, also known as Hansen's disease, is spread via the air by droplets released from an infected patient's nose and mouth. It is not transmitted through hugging, shaking hands, or sitting near an infected person. 

It is a treatable but neglected tropical illness that still affects more than 120 nations. If left untreated, the infection can cause nerve damage and disfigurement in certain situations.

So, how did cases begin to arise in the United States?

One probable source might be the emergence of new M. leprae strains, mainly M. lepromatosis.

Reportedly, cases of the recently identified strain have been detected in US patients. Some cases were reported by individuals who had traveled to places where leprosy is present or endemic.

Additionally, a common mammal in central Florida, nine-banded armadillos, which carry leprosy, could be a source of animal-to-human transmission. 

Carrie Kovarik, a professor of dermatology at the Hospital of the University of Pennsylvania, told the Guardian: “Although leprosy has been, and is still, uncommon in the US, there has been a change in the geography and epidemiology of the cases over the last decade.”

“Historically, the majority of patients in the US with leprosy lived or worked outside the country in disease-endemic areas and acquired their disease abroad or had prolonged contact with immigrants from leprosy-endemic countries; however, more recently, about one-third of people with leprosy in the US seem to have locally acquired the disease,” added Kovarik said. 

Experts aim to carry analyze the outdoor risk factor

A recent case of leprosy detected in a 54-year-old man proved to be quite atypical in central Florida. This single case analysis was reported in the journal Emerging Infectious Diseases this August.

This individual is a lifelong Florida resident, who had not traveled and had not come into touch with anyone known to have leprosy or any armadillos. He does, however, work as a landscaper and spends a lot of time outside.

The man's disease appears to have been acquired locally — similar to the roughly one-third (or 34 percent) of new leprosy cases identified in the United States between 2015 and 2020. 

"Our case adds to the growing body of literature suggesting that central Florida represents an endemic location for leprosy," mentioned the study authors in the paper. 

"By increasing local physician efforts to report the incidence and supporting further research to assess routes of transmission, a congruent effort can be made to identify and reduce the spread of the disease," added the study. 

According to experts, the transmission of this disease is likely far more convoluted than expected. 

The lack of established risk factors in this case as well as in other recent occurrences of leprosy in Florida — particularly in individuals spending time outdoors — has prompted experts to look into possible environmental reservoirs of this bacterial infection. 

Moreover, researchers aim to learn more about the incidence of M. lepromatosis infections and which animals transmit it to humans.

"It is perhaps remarkable that a new [bacterial] species causing an endemic disease of major public health impact has not prompted larger-scale studies to determine its true prevalence," the authors added.

Study abstract:

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. Travel to Florida should be considered when conducting leprosy contact tracing in any state.