venereal disease vs contagion

venereal disease and contagion both are nouns.

Word	Noun	Adjective	Verb	Adverb
venereal disease	Yes	No	No	No
contagion	Yes	No	No	No

As nouns, contagion is a hypernym of venereal disease; that is, contagion is a word with a broader meaning than venereal disease:

venereal disease: a communicable infection transmitted by sexual intercourse or genital contact
contagion: any disease easily transmitted by contact

Other hypernyms of venereal disease include contagious disease.

venereal disease (noun)	contagion (noun)
a communicable infection transmitted by sexual intercourse or genital contact	the communication of an attitude or emotional state among a number of people
	an incident in which an infectious disease is transmitted
	any disease easily transmitted by contact