The mid-3rd century saw a period of cooling and drought, well documented in many regions. During previous years of drought, the exceptional ecological conditions of the fertile Nile valley had helped the Roman authorities to overcome famine in other regions, but the floods of the Nile were abnormally weak from 244 to 248. Furthermore, the deadly pandemic now known as the Plague of Cyprian first hit the Mediterranean in 249. Cyprian, Bishop of Carthage, after whom the plague is named, attributed the calamities to the "old age of the world", but the pagans blamed the Christians' reluctance to worship the ancient gods. The size of the Christian communities had significantly grown in large urban centers like Rome, Antioch, Alexandria and Carthage in the early 3rd century. Regarded the opponents of traditional Roman values the Christians were outlawed, but they were only sporadically persecuted. A drastic change came with Emperor Decius' edict compelling all Romans to make sacrifices to the gods in 249. Non-compliant Christians were executed or forced into exile and the purge continued until Emperor Gallienus put an end to it in 260.