Leprosy was virtually non-existent in the USA for many decades. The tiny number of cases were generally attributed to zoonotic transmission from armadillos in the Southwestern USA.
However, in the early 1980s, cases of leprosy were identified among immigrant men in New York City. These were believed to have been non-autochthonous, meaning they acquired the infection somewhere else before moving to New York City. Then in 2000, New York City had its first case of an autochthonous (locally acquired) leprosy infection.
Now, Central Florida is reporting a surge in new leprosy infections. These are not believed to be the result of zoonotic transmission from armadillos but from person-to-person transmission within the United States.
A new paper in the August 2023 issue of Emerging Infection Diseases, published on the CDC website, suggests mass immigration is fueling a rise in new autochthonous leprosy infections.
Central Florida, in particular, accounted for 81% of cases reported in Florida and almost one fifth of nationally reported cases (3). Whereas leprosy in the United States previously affected persons who had immigrated from leprosy-endemic areas, ≈34% of new case-patients during 2015–2020 appeared to have locally acquired the disease (4). Several cases in central Florida demonstrate no clear evidence of zoonotic exposure or traditionally known risk factors. We report a case of lepromatous leprosy in central Florida in a man without risk factors for known transmission routes. We also review the mounting epidemiologic evidence supporting leprosy as an endemic process in the southeastern United States.
Given those reports, there is some support for the theory that international migration of persons with leprosy is a potential source of autochthonous transmission. Reports from Spain linked an increase in migration from other countries to an increase in autochthonous leprosy (7). The number of international migrants in North America increased from 27.6 million persons in 1990 to 58.7 million in 2020 (8), so a link to migration may account for the increase in incidence of leprosy in historically nonendemic areas. Further, reports from the Centers for Disease Control and Prevention 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 (Appendix Figure) (9). This information suggests that leprosy has become an endemic disease process in Florida, warranting further research into other methods of autochthonous transmission.
From CDC website, dated 2017: (Must be downloaded to be read)
In 1982, we reported that leprosy in New York City occurred exclusively among foreign-born persons (1). In 1991, Mastro et al. reported that leprosy was an epidemic phenomenon without secondary transmission (2). In 2000, however, the first autochthonous cases of leprosy in New York City were reported (3), and 2 additional autochthonous cases subsequently were reported (4,5). Autochthonous leprosy has been reported in the eastern United States in Georgia (6) and central Florida (7); transmission was blamed on armadillos, even though most of these case-patients had no history of exposure to armadillos, and armadillos east of the Mississippi River rarely have leprosy (8). Although the transmission of leprosy is poorly understood, international migration of persons with leprosy is a more likely scenario for autochthonous transmission than contact with armadillos, especially if a case-patient has no history of armadillo exposure. Ramos et al. linked an increase in autochthonous leprosy in Spain to a 5-fold increase in migration from countries where leprosy is prevalent (9). There are no wild armadillos in New York City. Autochthonous cases of leprosy reported from the eastern United States should not be assumed to be from armadillos. Physicians throughout the United States need to be aware that leprosy can occur in native-born Americans and that delayed diagnosis, which occurs frequently, can result in unacceptable deformities.