History of the Peloponnesian War

At the very beginning of the next summer the Peloponnesians and their allies, with two thirds of their forces, as on the first occasion, invaded Attica, under the command of Archidamus, the son of Zeuxidamus, king of the Lacedaemonians; and after encamping, they laid waste the country.

When they had not yet been many days in Attica, the plague first began to show itself amongst the Athenians; though it was said to have previously lighted on many places, about Lemnos and elsewhere. Such a pestilence, however, and loss of life as this was no where remembered to have happened.