plague vs infestation

plague and infestation both are nouns.

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

As nouns, plague and infestation are synonyms defined as:

plague (noun)	infestation (noun)
an annoyance	a swarm of insects that attack plants
any large scale calamity (especially when thought to be sent by God)	the state of being invaded or overrun by parasites
a swarm of insects that attack plants
a serious (sometimes fatal) infection of rodents caused by Yersinia pestis and accidentally transmitted to humans by the bite of a flea that has bitten an infected animal
any epidemic disease with a high death rate

plague (verb)	infestation (verb)
annoy continually or chronically
cause to suffer a blight