swarm vs infestation

swarm and infestation both are nouns.

Word	Noun	Adjective	Verb	Adverb
swarm	Yes	No	Yes	No
infestation	Yes	No	No	No

As nouns, infestation is a hyponym of swarm; that is, infestation is a word with a more specific, narrower meaning than swarm:

Other hyponyms of swarm include plague.

swarm (noun)	infestation (noun)
a group of many things in the air or on the ground	a swarm of insects that attack plants
a moving crowd	the state of being invaded or overrun by parasites

swarm (verb)	infestation (verb)
move in large numbers
be teeming, be abuzz