Green’s Dictionary of Slang

(US) a venereal disease.

1926		‘Turkey in the Straw’ in Canfield Coll. Here’s to the Kaiser, the son of a bitch/ May he die of the pox and the seven year’s itch.
c.1949		in E. Cray Erotic Muse (1992) 184: He had blue balls and the seven-year itch. / He had the clap and the syphilis too.