David Biello in Scientific American:
More than 2,000 years ago, a plague gripped the Greek city of Athens. Ultimately, as much as a third of the population succumbed and the devastation, which helped Sparta gain the upper hand in the nearly 30-year-long war between the city-states. That much Thucydides–an ancient historian, general in the war and plague victim who recovered–conveys in his History of the Peloponnesian War. But he did not leave a precise enough description to decide definitively whether the disease was bubonic plague, smallpox or a host of other ailments. Now DNA collected from teeth in an ancient burial pit points to typhoid fever.