Leprosy, Florida's New Ancient Plague

Woe be unto us

Aug 02, 2023

From the biblical book of Leviticus:

⁴³The priest is to examine him, and if the swollen sore on his head or forehead is reddish-white like a defiling skin disease, ⁴⁴the man is diseased and is unclean. The priest shall pronounce him unclean because of the sore on his head.
⁴⁵“Anyone with such a defiling disease must wear torn clothes, let their hair be unkempt,cover the lower part of their face and cry out, ‘Unclean! Unclean!’ ⁴⁶As long as they have the disease they remain unclean. They must live alone; they must live outside the camp.1

These verses of the Bible are probably talking about leprosy. Leprosy has been an awful disease afflicting humanity since before recorded history. It’s a contagious disease and here’s what the CDC says about its spread (it’s also called Hansen’s disease):

It is not known exactly how Hansen’s disease spreads between people. Scientists currently think it may happen when a person with Hansen’s disease coughs or sneezes, and a healthy person breathes in the droplets containing the bacteria. Prolonged, close contact with someone with untreated leprosy over many months is needed to catch the disease.2

Around the world leprosy was seen as a sentence where victims were separated from family to wait for death. As late as 1969 Hawaii still forced lepers to live in a colony called Kalaupapa on the island of Molokai.

Hey, if you gotta be quarantined … Map Courtesy CNN

It’s an old disease that stays slightly active on the radar screen. Not really a big deal. But then I was puzzled by the following CBS News headline: Leprosy could be endemic in Central Florida, CDC says. What to know about the disease.

The broad outlines of how leprosy works has been known for some time. The Cleveland Clinic says it’s caused by the bacteria Mycobacterium leprae. It’s curable with a ~~coattail~~ cocktail of antibiotics. But it’s usually not detected early since it can stay dormant in a victim for decades.

Medieval lepers required to ring bell to warn people away. Picture Via Wikimedia Commons

There are only 4 animals known to spread leprosy — Humans, European red squirrel, chimpanzees and armadillos. Florida has no European red squirrels or chimpanzees but lots of humans and armadillos.

So, the US has about 150 cases per year, with Florida contributing about 30 of these or 20% of the cases in a given year. In a population of 22.3 million that still doesn’t sound like a big deal. When I looked closer into the case distribution it became clearer that Florida doesn’t have a problem with leprosy. But one county does.

Brevard County is Florida’s is the 10th largest county by population. Its population of 631,000 accounts for only 2.8% of the state’s population. But they make up over 74% of the total leprosy cases3.

**Brevard is the Leprosy Capital of Florida**

This proportion of cases in Brevard County has remained pretty constant over the years. So what’s going on here? Why has Brevard County remained the king of leprosy for over a decade now.

I have 4 possible explanations for Brevard County seeing an elevated incidence of leprosy for an extended period of time. I’m going to list each of these and discuss it briefly.

It’s brought in from other places. There are many more cases of leprosy worldwide than in Florida. India reported 75,394 cases in 2021. Several other countries reported cases in excess of 10,000, dwarfing Florida’s 150 cases. Could the cases be from people immigrating from or visiting countries with a higher incidence? My guess is no. If it’s being brought from abroad then why Brevard? Sure, there are lots of brainy folks from around the world working at Kennedy Space Center, but Orlando also has lots of brainy people from elsewhere. And Miami. And lots of other places. Why aren’t they similarly affected. Probability 5%.
It’s circulating in a small community that has little contact with the outside. This community is passing the disease among its members. These small communities, usually religious in nature, sometimes cut off contact with the outside world to keep themselves pure. In this case they’re passing leprosy but may not even understand they’re doing it since the incubation period for leprosy can be measured in decades. That’s possible, but I think we would have heard about this is it were an issue in a self-isolating community. There used to be religious communities that kept away from others, but there just aren’t that many in Florida these days. I’m skeptical. Probability 15%.
There’s a reservoir of leprosy in the armadillo population that’s occasionally infecting people. For some reason most of the literature go out of their way to say that armadillos usually don’t infect people, but I couldn’t find a good discussion of why it is rare. Armadillos have been eaten in both the US and lots of other places over the years. They were called Hoover Hogs during the depression. If they have become a reservoir for the disease and Florida Man is testing to see if they taste like chicken this could be the reason. But I still only give it a 30% chance of being correct.
Guilty as Charged? Photo by Cindy Buckland
It’s a reporting artifact. In my many years working as a corporate statistician I found that most really strange pieces of information could be explained as misunderstood data. It’s possible that lots of leprosy occurring in other counties are for some reason reported as being in Brevard County. Maybe there’s one Brevard doctor that is the state specialist in leprosy that does the state reporting when doctors that have never seen it call for a consult. Or maybe there’s a state employee in Brevard County whose job it is to look for infectious disease. Or maybe there’s a doctor in Brevard that’s misdiagnosing another disease as leprosy. I give this a 50% chance of being correct.

So, where does that leave us? While I consider alternative #4 to be the most likely #3 is the scary one. If leprosy is endemic in armadillos and if they are easily passing the disease to humans it’s going to be a long time before it can be completely controlled. The armadillo population is large and and their nocturnal habits keep them relatively hidden (aside from roadkill victims).

I write these pieces mostly to organize a topic in my own mind. Sometimes I can come to a firm conclusion of what’s going on. Sometimes not. This is somewhere in between. I think the issue is a reporting issue. But I’m not completely sure. I hope it’s not being passed relatively easily from armadillos to humans. If that’s true it will be a long time before it leprosy once again becomes a disease only encountered in the Bible.

So, what have I missed? Is there another possibility in addition to the 4 above? Are my probabilities off. Let me know in the comments.

Naturalist with Numbers

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