The Plague of Athens was an epidemic which hit the city-state of Athens in ancient Greece during the second year of the Peloponnesian War (430 BC), when an Athenian victory still seemed possible. Many historians believe that it entered Athens through Piraeus, the city's port and sole source of food and supplies. The city-state of Sparta, and much of the eastern Mediterranean, was also struck by the disease. The plague returned twice more, in 429 BC and in the winter of 427/6 BC.