Leprosy is an ancient disease. References to leprosy and the social stigma attached to it go back to 600 BC from India and in the Old Testament. However, like the plague, it was not until relatively late (1873) that the term leprosy became attached to a particular microbe, Mycobacterium leprae. Although some medieval descriptions suggest M. leprae, it can be very difficult to sort true leprosy from other skin conditions in medieval texts. This is where paleomicrobiology and biological anthropology come in.
Bioarchaeologists have been able to identify skeletal changes suggestive of M. leprae for some time. These changes only occur in the most severe cases making it unclear how common true leprosy was in ancient and medieval times. It takes many years, if not decades, for leprosy to cause skeletal changes. As with many chronic infectious diseases, it is likely that more people died with the disease than from it. Another way to assess the level and origins of ancient and medieval leprosy is by looking at ancient DNA.
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