If a Scorpion Hugged an Armadillo, would it contract Leprosy?

Of all the infectious diseases in history, one that has gotten an unwarranted bad rap is leprosy, or Hansen's Disease. This disease, which is mentioned in the bible, has become synonymous with contagion--but it's not really a very contagious disease at all. 

Hansen's Disease, caused by infection with Mycobacterium leprae (and also M.lepromatosis), is a chronic disease that effects the respiratory system nerves, skin, and mucus membranes. It is by no means incurable as it is amenable to treatment with antibiotics. It is spread from person-to-person via the respiratory route. It's natural host is the armadillo. In 2009, a little over 200 new cases were reported in the US.

What most people don't realize however, is that 95% of humans are unable to be infected because of a specific genetic resistance conferred via their immune systems.  This means that far from being highly contagious, leprosy's transmissibility between humans is seriously hobbled. 

All of these facts have been known for sometime but it didn't stop the creation of leper colonies (e.g. Molokai in Hawaii) or other unjustified control measures in the not too far past. These misconceptions persist to this day and have penetrated deeply into popular culture. Case in point: the television program Scorpion. On a recent episode, one character states to another that he hugs as if he's at a leper colony. Such a comment is based on an extremely erroneous notion of leprosy's contagiousness.

What this brief mention on a tv program illustrates is the need to educate people on the difference between highly contagious infectious diseases and those that are less contagious. Such a point was something that I sought to make, over and over, with Ebola lest unjustified control measures be instituted as they were with leprosy. 

Don't Fear the Leper

Leprosy, or Hansen's Disease, is a term that strikes fear into the heart of everyone, almost exclusively in those who know little about the disease. Since biblical times, lepers were casted outside of society and interaction with them was minimized. Leper colonies were created, even in the US. 

One of the most infamous of these colonies was on the island of Molokai in Hawaii. This colony, which was the result of a forced segregation policy, lasted for over 100 years until 1969. This colony has been the subject of at least two books and a film focused on the experiences of Father Damien, a  Catholic priest who resided there and ultimately became infected, was also made. I saw the film last night and found it interesting and instructive to those interested in the history of this disease.

However, leprosy is not easily spread between humans and since the 1940s--prior to the ending of forced segregation--effective antibiotic treatment has been available. In my experience, I have only known of one case in the Pittsburgh area in an immigrant, who did not spread it further. 

Like HIV thousands of years later, leprosy illustrates that fear of infectious disease has been a recurrent theme and will likely continue so long as novel infectious diseases continue to appear--a safe bet.