# virulence

/ˈvɪɹəɫəns/ (US) · /vˈɪɹələns/ (UK) · CEFR C2 · Noun

Source: https://englishreference.com/word/virulence
Updated: 2026-10-19

## Definition

how strong and harmful a germ is — how much damage it can do when it makes people sick.

For teachers: degree to which a pathogen causes severe disease in a host organism. Reflects infectivity, replication rate, and ability to overcome host defences.

## Examples

- Doctors study the virulence of new flu strains.
- The lab compares the virulence of two variants to see which causes more severe illness in mice.
- Despite its rapid spread, the new strain shows reduced virulence, causing milder symptoms than earlier variants that overwhelmed hospitals.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.