As in Mosiah 7:31, the Hebrew idiom, the east wind, is used. This phrase means a destruction or a famine. The expression is used many times in the Old Testament. From Easton's Bible Dictionary, "In Palestine this wind blows from a burning desert, and hence is destitute of moisture necessary for vegetation."
"The east wind is a destructive wind which originates in the east, the symbolic direction of Deity's presence. Also called 'the wind of the Lord' (Hosea 13:15), it is 'prepared' by God (Jonah 4:8) for the purpose of destroying the ungodly and unrighteous. The Lord has stated, 'If my people shall sow filthiness they shall reap the east wind, which bringeth immediate destruction' (Mosiah 7:31). Hence they are 'smitten with the east wind' (Mosiah 12:6; see also Job 27:21)." (Donald W. Parry, Joseph Fielding McConkie, A Guide to Scriptural Symbolism, p. 45)