actively poisonous; intensely noxious

a virulent insect bite.

Medicine/Medical . highly infective; malignant or deadly.

Bacteriology . causing clinical symptoms.

violently or spitefully hostile.

intensely bitter, spiteful, or malicious

a virulent attack.

adjective

harmless , healthy , nonpoisonous , gentle , kind , nice

adjective

baneful , deadly , destructive , fatal , harmful , infective , injurious , malign , malignant , mephitic , pernicious , poison , septic , toxic , toxicant , unhealthy , unwholesome , venomous , acrimonious , antagonistic , bitter , cutting , hateful , malevolent , malicious , rancorous , resentful , scathing , sharp , spiteful , splenetic , stabbing , unfriendly , vicious , vindictive , vitriolic , noxious , pestilent , pestilential , mephitical , embittered , hard , harsh , hostile , infectious , irritating , lethal , obnoxious , poisonous , sarcastic