For the plague broke out as soon as the Peloponnesians invaded Attica, and never entering Peloponnese (not at least to an extent worth noticing), committed its worst ravages at Athens, and next to Athens, at the most populous of the other towns.
Such was the history of the plague.
After ravaging the plain, the Peloponnesians advanced into the Paralian region as far as Laurium, where the Athenian silver mines are, and first laid waste the side looking towards Peloponnese, next that which faces Euboea and Andros.

But Pericles, who was still general, held the same opinion as in the former invasion, and would not let the Athenians march out against them.
However, while they were still in the plain, and had not yet entered the Paralian land, he had prepared an armament of a hundred ships for Peloponnese, and when all was ready put out to sea.

On board the ships he took four thousand Athenian heavy infantry, and three hundred cavalry in horse transports, and then for the first time made out of old galleys; fifty Chian and Lesbian vessels also joining in the expedition.
When this Athenian armament put out to sea, they left the Peloponnesians in Attica in the Paralian region.

Arriving at Epidaurus in Peloponnese they ravaged most of the territory, and even had hopes of taking the town by an assault: in this however they were not successful.

Putting out from Epidaurus, they laid waste the territory of Troezen, Halieis, and Hermione, all towns on the coast of Peloponnese, and thence sailing to Prasiai, a maritime town in Laconia, ravaged part of its territory, and took and sacked the place itself; after which they returned home, but found the Peloponnesians gone and no longer in Attica.
During the whole time that the Peloponnesians were in Attica and the Athenians on the expedition in their ships, men kept dying of the plague both in the armament and in Athens.