Virulence, Virulency, n.
Etymology: [Cf. F. virulence, L. virulentia an offensive odor, a stench.]
1. The quality or state of being virulent or venomous; poisonousness; malignancy.
2. Extreme bitterness or malignity of disposition. "Refuted without satirical virulency." Barrow. The virulence of one declaimer, or the profundities and sublimities of the other. I. Taylor.
Shades of meaning
Fernald has no entry of its own for virulence; he lists it under acrimony.
Where he writes about it:
Malignity is the extreme of settled ill intent; virulence is an envenomed hostility. — from acrimony
Virulence of speech is a quality in language that makes the language seem as if exuding poison. — from acrimony
Virulence is outspoken; malignity may be covered with smooth and courteous phrase. — from acrimony
We say intense virulence, deep malignity. — from acrimony