The Medievalist and the Microbiologist: How Plague and Leprosy Have Opened Up New Perspectives on the History of Health

[Plenary Lecture given on *May 27, 2012* at the Canadian Society for the History of Medicine Annual Conference, University of Waterloo]

Monica Green, an Arizona State University professor known as “the foremost authority on medicine in the Middle Ages,” examines how her field has changed in recent years. In 2001, two genetic breakthroughs were made – the entire genomes for both plague
(Yersinia pestis) and leprosy (Mycobacterium leprae) were sequenced.

Microbiology/genetic analyses have so far proven to be very beneficial at answering some questions, such as: What was the disease?; How old is the disease?; Where did it come from?  Paleopathology (the study of old bones) is a bigger factor in the determining the history of leprosy – this science is often not good at certain diseases, but for leprosy it is very good at finding lesions, such as at nasal cavity.  Our generic understanding of leprosy has allowed us to identify the oldest DNA in an individual, a skeleton from Uzbeckistan that is dated between 1st to 4th century AD. The disease’s organism is now thought to several million years old, and the organism has stopped evolving because it so comfortable in human populations.

But certain questions remain to be answered: How many were afflicted? How did people respond? Green notes one particular problem with our understanding of leprosy: Why did it ‘suddenly’ become a social problem in Europe in the 11/12th century.

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