canker

nouns

a fungal disease of woody plants that causes localized damage to the bark
is a type of (narrower)
a disease that affects plants
an ulceration (especially of the lips or lining of the mouth)
is derived from
a pernicious and malign influence that is hard to get rid of
"racism is a pestilence at the heart of the nation"; "according to him, I was the canker in their midst"

verbs

become infected with a canker
is a type of (narrower)
get sick
"She fell sick last Friday, and now she is in the hospital"
infect with a canker
is a type of (narrower)
communicate a disease to
"Your children have infected you with this head cold"