Last year it was Ebola in West Africa, and now it’s MERS in Korea. If you worry about an impending pandemic, you are surely not alone. Yet humanity had faced and survived many far more severe pandemics, such as the plague that caused the Black Death in 14th century Europe. The Black Death killed at least one-third of the European populations the. Today, with bacteriologist Prof Thomas Hugh Pennington, we explore where the plague came from, how it kills, and why scientists are still concerned