Pelusium
A city at the easternmost mouth of the Nile, on the road between Egypt and Palestine.
Today: Tell el-Farama, Egypt
The Plague at Constantinople
Procopius, History of the Wars, Book 2 (chapters 22–23) · c. 550 (events of 542; Books 1–7 made public in 551 at the earliest)
Ἤρξατο μὲν ἐξ Αἰγυπτίων οἳ ᾤκηνται ἐν Πηλουσίῳ. γενομένη δὲ δίχα πὴ μὲν ἐπί τε Ἀλεξανδρείας καὶ τῆς ἄλλης Αἰγύπτου ἐχώρησε, πὴ δὲ ἐπὶ Παλαιστίνους τοὺς Αἰγυπτίοις ὁμόρους ἦλθεν, ἐντεῦθέν τε κατέλαβε τὴν γῆν σύμπασαν, ὁδῷ τε ἀεὶ προϊοῦσα καὶ χρόνοις βαδίζουσα τοῖς καθήκουσιν.
It began among the Egyptians who live in Pelusium. From there it split in two. One branch moved toward Alexandria and the other parts of Egypt, while the other came to the Palestinians, Egypt's neighbors. From there it took hold of the whole earth, always moving forward along its road and traveling at its appointed times.