virus: virulent (vir-yuh-luhnt): Something or someone that is highly infective, malignant(muh-lig-nuhnt)or deadly.

vir·u·lent·ly, adverb
hy·per·vir·u·lent, adjective
hy·per·vir·u·lent·ly, adverb
non·vir·u·lent, adjective
non·vir·u·lent·ly, adverb
su·per·vir·u·lent, adjective
su·per·vir·u·lent·ly, adverb
un·vir·u·lent, adjective
un·vir·u·lent·ly, adverb