Definition of virulence
: the quality or state of being virulent: such as
a
: extreme bitterness or malevolence : rancor
the virulence of their hatred She said the rising virulence of the rhetoric against Muslims has flooded her with sadness, grief, alienation and fear.— Laura DaSilva But the virulence of the campaign, on both sides … provides a clue to the deeper forces at work: the polarizing of politics in a traditionally moderate place. — The Economist
b
: the relative capacity of a pathogen (such as a bacterium or virus) to overcome a host's defenses and cause disease or damage : the degree of pathogenicity of a causative agent of disease
a bacterial strain of low virulence the virulence of a novel virus
also
: the ability to overcome a host's defenses and cause disease or damage : the state of being pathogenic
With its newly acquired virulence, this otherwise mild-mannered avian influenza virus went wild. — Rick Weiss
c
: relative severity or malignancy
Breast cancer is as diverse as the breast itself, appearing in many different guises. Some cancers seem to erupt out of ordinary breast issue with an awesome virulence, spreading rapidly throughout the body.— David Plotkin
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Merriam-Webster unabridged
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Time Traveler for virulence
The first known use of virulence was in 1597
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