Increases in the competitive fitness of West Nile virus isolates after introduction into California

Gabriella Worwa, Andra A. Hutton, Michèle Frey, Nisha K. Duggal, Aaron Brault, William Reisen

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


To investigate the phenotypic evolution of West Nile virus (WNV) in California, we competed sixteen isolates made during 2007–08 against COAV997-5nt, a genetically marked clone from the founding 2003 California isolate COAV997-2003. Using in vivo fitness competitions in House Finches (HOFI) and Culex tarsalis mosquitoes, we found that the majority of WNV WN02 and SW03 genotype isolates exhibited elevated replicative fitness in both hosts compared to COAV997-5nt. Increased replicative capacity in HOFIs was not associated with increased mortality, indicating that these isolates had not gained avian virulence. One WN02 isolate from Coachella Valley, a region geographically close to the isolation of COAV997, showed neutral fitness in HOFIs and reduced fitness in Cx. tarsalis. Two isolates from Kern County and Sacramento/Yolo County out-competed COAV997-nt in HOFIs, but were transmitted less efficiently by Cx. tarsalis. Competition demonstrated neutral or increased fitness that appeared independent of both WN02 and SW03 genotypes.

Original languageEnglish (US)
Pages (from-to)170-181
Number of pages12
StatePublished - Jan 15 2018


  • California
  • Competitive fitness
  • Evolution
  • Genotype
  • Invasion
  • Phenotype
  • West Nile virus

ASJC Scopus subject areas

  • Virology


Dive into the research topics of 'Increases in the competitive fitness of West Nile virus isolates after introduction into California'. Together they form a unique fingerprint.

Cite this