Enhanced fitness of SARS-CoV-2 B.1.617.2 Delta variant in ferrets

Virology. 2023 May:582:57-61. doi: 10.1016/j.virol.2023.03.014. Epub 2023 Apr 5.


Competition assays were conducted in vitro and in vivo to examine how the Delta (B.1.617.2) variant displaced the prototype Washington/1/2020 (WA/1) strain. While WA/1 virus exhibited a moderately increased proportion compared to that in the inoculum following co-infection in human respiratory cells, Delta variant possessed a substantial in vivo fitness advantage as this virus becoming predominant in both inoculated and contact animals. This work identifies critical traits of the Delta variant that likely played a role in it becoming a dominant variant and highlights the necessities of employing multiple model systems to assess the fitness of newly emerged SARS-CoV-2 variants.

Keywords: Delta variant; Ferrets; SARS-CoV-2; Viral fitness.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Biological Assay
  • COVID-19*
  • Ferrets*
  • Humans
  • SARS-CoV-2 / genetics

Supplementary concepts

  • SARS-CoV-2 variants