The Second Plague Pandemic of the mid-14th century, also known as the Black Death, killed 30–60% of the European population and profoundly changed the course of European history. New research led by Penn State and the University of Adelaide suggests that this plague, potentially through resulting changes in diet and hygiene, may also be associated with a shift in the composition of the human oral microbiome toward one that contributes to chronic diseases in modern-day humans.
