Evolution of virulence when transmission occurs before disease

Erik E. Osnas, Andrew P. Dobson

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Most models of virulence evolution assume that transmission and virulence are constant during an infection. In many viral (HIV and influenza), bacterial (TB) and prion (BSE and CWD) systems, disease-induced mortality occurs long after the host becomes infectious. Therefore, we constructed a model with two infected classes that differ in transmission rate and virulence in order to understand how the evolutionarily stable strategy (ESS) depends on the relative difference in transmission and virulence between classes, on the transition rate between classes and on the recovery rate from the second class. We find that ESS virulence decreases when expressed early in the infection or when transmission occurs late in an infection. When virulence occurred relatively equally in each class and there was disease recovery, ESS virulence increased with increased transition rate. In contrast, ESS virulence first increased and then decreased with transition rate when there was little virulence early in the infection and a rapid recovery rate. This model predicts that ESS virulence is highly dependent on the timing of transmission and pathology after infection; thus, pathogen evolution may either increase or decrease virulence after emergence in a new host.

Original languageEnglish (US)
Pages (from-to)505-508
Number of pages4
JournalBiology Letters
Issue number4
StatePublished - Aug 23 2010

All Science Journal Classification (ASJC) codes

  • General Agricultural and Biological Sciences
  • Agricultural and Biological Sciences (miscellaneous)


  • Emerging disease
  • Evolution
  • Evolutionarily stable strategy
  • Virulence
  • Wildlife


Dive into the research topics of 'Evolution of virulence when transmission occurs before disease'. Together they form a unique fingerprint.

Cite this