Maran Vit. Bas. l. c. says that these words cannot refer to the persecution of Valens in Cappadocia in 371, for that persecution went on between Constantinople and Cappadocia, and did not start from the East.  There need be no surprise, he thinks, at the two preceding letters containing no mention of this persecution, because Acacius, who was a native of Bera, would be sure to report all that he had observed in Cappadocia.  I am not sure that the reference to a kind of prairie fire spreading from the East does not rather imply a prevalence of heresy than what is commonly meant by persecution.  Meletius, however, was banished from Antioch in 374 and Eusebius from Samosata in the same year, as graphically described by Theodoret H.E. iv. 13.