From 430 to 426 B.C.E., a great plague swept through the city-state of Athens. The historian Thucydides describes the symptoms this way:
People in good health were all of a sudden attacked by violent heats in the head and the throat or tongue, becoming bloody and emitting an unnatural and fetid breath. When it fixed in the stomach, it upset it; and discharges of bile of every kind named by physicians ensued, accompanied by very great distress. If they passed this stage, and the disease descended further into the bowels, inducing a violent ulceration there accompanied by severe diarrhea, this brought on a weakness which was generally fatal.
What was the cause of this plague?