Cases of This Ancient Infectious Disease Are Currently Surging in the US

New cases of leprosy have steadily risen in recent years.

Originally Published: 
Illustration of Mycobacterium leprae, a gram-positive bacteria which is the cause of leprosy (Hansen...

Leprosy is a centuries-old infectious disease often perceived as firmly affixed to an ancient, more fearful time. But this week’s news shows that couldn’t be further from the truth: A new report from the Centers for Disease Control warns that leprosy is surging in the US, particularly in Central Florida, which may have become an “endemic location.”

In the southern US, leprosy (later known as Hansen’s disease) had spread between the sixteenth and eighteen centuries, with the first documented case in Louisana in 1758.

"Leprosy has been historically uncommon in the United States; incidence peaked around 1983, and a drastic reduction in the annual number of documented cases occurred from the 1980s through 2000," the report’s authors wrote. "However, since then, reports demonstrate a gradual increase in the incidence of leprosy in the United States. The number of reported cases has more than doubled in the southeastern states over the last decade."

There were 159 leprosy cases documented in the US in 2020, with Florida among the most reported state, according to the National Hansen’s Disease Program. Central Florida has accounted for 81 percent of the state’s cases and one-fifth of those nationally reported. For reference, more than 200,000 cases of leprosy are reported every year in more than 120 countries, according to the World Health Organization.

What causes leprosy, and how does it spread?

The chronic infectious disease is caused by the bacterium Mycobacterium leprae, a slow-growing microbe that damages peripheral nerves, skin, eyes, nose, and muscles over many years, eventually leading to visible physical deformities among those affected. Symptoms include discolored, thick, or dry skin; muscle weakness or paralysis; and blindness in the most severe, untreated cases.

In the wild, armadilloes, such as the nine-banded armadillo, are one of the only known carriers. It’s possible, although very low risk, to contract the bacteria from them.

More typically, leprosy can spread by extended contact with an infected individual, although scientists are exactly sure how the mechanics of that work. There’s some thought that, over an extended period of time, when an infected person coughs or sneezes, the healthy person breathes in respiratory droplets laden with bacteria.

In Central Florida, however, public health officials haven't nailed down how leprosy is spreading. It doesn't seem to be linked to a particular animal. It could be spreading from visitors coming in from other countries where leprosy is endemic, but there isn't strong evidence for that either, according to the CDC report.

The good news is that leprosy is not what it used to be. With early diagnosis and treatment, the condition is now completely curable. (Treatment does not reverse extensive damage in advanced stages of the disease, though.) The recommended treatment involves a triple course of three drugs – dapsone, rifampicin, and clofazimine — which stop Mycobacterium leprae from growing.

“Our case adds to the growing body of literature suggesting that central Florida represents an endemic location for leprosy,” wrote the report’s authors. “Travel to this area, even in the absence of other risk factors, should prompt consideration of leprosy in the appropriate clinical context.”

This article was originally published on

Related Tags