What does virulence mean?
Virulence is the degree to which a microorganism or other pathogen can cause disease, serious harm, or tissue damage. It is distinct from pathogenicity, which broadly describes the ability to cause disease: virulence more precisely indicates how severe, aggressive, or damaging the resulting disease can be. The term is common in microbiology, epidemiology, medicine, and discussions of emerging infections. It can also be used more broadly, though less frequently, for viciousness, poisonousness, or intense hostility, especially in formal or literary contexts. Saying that a strain has increased in virulence suggests that it has become more harmful, not merely that it is more transmissible. Virulence is therefore useful when discussing the relative danger posed by pathogens, the effects of mutations, and the severity of infectious disease.
nounThe degree to which a pathogen can cause disease, severe harm, or tissue damage. More broadly, it can refer to the quality of being vicious, poisonous, or intensely hostile.
- The degree to which a pathogen can cause disease or severe harm.
- The quality of being vicious, poisonous, or intensely hostile.
"The researchers found that mutations had increased the virulence of the bacterium."
"Rapid mutation allowed the pathogen to increase in virulence and cause more severe infections."
"He recoiled from the virulence of her criticism."
The plural is uncommon and is used mainly when comparing different degrees of harmful or disease-producing power.
"The study compared the virulences of the two bacterial strains."
Virulence turns a germ's identity into a measure of harm: the same species can be mild in one person and ferocious in another.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does virulence come from?
Virulence entered English through Latin virulentia, a noun formed from virulentus, meaning “poisonous” or “malignant,” which derives from the Latin word virus, meaning “poison” or “slime.” In early English, the word referred broadly to a poisonous or malign quality, while its now-dominant medical sense became especially established with the study of infectious disease. Its English relatives include virulent, virology, and virologist, all of which continue the same Latin root.
Related word forms
How virulence is actually used
In medicine and microbiology, virulence is a formal technical term for the degree of pathogenic harm an organism can cause. Its broader sense involving viciousness or extreme hostility is less common and often has a strongly negative or literary tone.
Easily confused with virulence
Virulence is the noun naming a degree of harmful or disease-producing power, whereas virulent is the adjective describing something that is harmful, poisonous, or capable of causing severe disease.