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Composite virulence: useful metric or conceptual trap?
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Authors
Luis M. Silva 
,
Tiago G. Zeferino
Abstract
Virulence, defined as the harm an infection causes to its host, is central to evolutionary ecology, yet it remains difficult to quantify because infection impact is multidimensional, dynamic, and context-dependent. Composite measures have therefore emerged to summarise multiple traits into a single estimate of infection-induced harm. However, every composite embeds biological assumptions about which traits represent virulence, how they relate to one another, and which components of harm are prioritised. When these assumptions remain implicit, composites can obscure causal mechanisms and compromise interpretation. We argue that composite virulence should be treated as a biologically-grounded measurement strategy rather than a definition of virulence. Used transparently, composite approaches can strengthen evolutionary inference; used carelessly, they risk concealing rather than clarifying infection biology.
DOI
https://doi.org/10.32942/X25654
Subjects
Animal Diseases, Animal Experimentation and Research, Animal Sciences, Biodiversity, Biology, Ecology and Evolutionary Biology, Evolution, Immunity, Immunology and Infectious Disease, Immunology of Infectious Disease, Immunopathology, Life Sciences, Medical Microbiology, Microbiology, Other Ecology and Evolutionary Biology, Other Immunology and Infectious Disease, Parasitic Diseases, Parasitology, Pathogenic Microbiology, Plant Pathology, Research Methods in Life Sciences, Zoology
Keywords
virulence, composite virulence, life history, composite index, host-parasite, host-pathogen, infectious diseases
Dates
Published: 2026-02-21 02:29
Last Updated: 2026-07-17 16:53
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License
CC-BY Attribution-NonCommercial 4.0 International
Additional Metadata
Conflict of interest statement:
None
Data and Code Availability Statement:
Not applicable
Language:
English
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