From The National Geographic:
An ancient medical mystery—the cause of a plague that wracked Athens from 426 to 430 B.C. and eventually led to the city’s fall—has been solved by DNA analysis, researchers say. The ancient Athenians died from typhoid fever, according to a new study. Scientists from the University of Athens drew this conclusion after studying dental pulp extracted from the teeth of three people found in a mass grave in Athens’ Kerameikos cemetery.
Researchers believe the plague may have been the result of a military strategy devised by the Athenians’ leader, Pericles. To counter an offensive by the Spartans, Pericles evacuated parts of the Athenian territory and sheltered its citizens behind Athens’ fortifications. Gathering tens of thousands of people in overcrowded and unsanitary conditions created the perfect atmosphere in which infectious disease could spread, researchers say.
More here.