Emerging Infectious Diseases (May 2012)

Characterization of Virulent West Nile Virus Kunjin Strain, Australia, 2011

  • Melinda J. Frost,
  • Jing Zhang,
  • Judith H. Edmonds,
  • Natalie A. Prow,
  • Xingnian Gu,
  • Rodney Davis,
  • Christine Hornitzky,
  • Kathleen E. Arzey,
  • Deborah Finlaison,
  • Paul Hick,
  • Andrew Read,
  • Jody Hobson-Peters,
  • Fiona J. May,
  • Stephen L. Doggett,
  • John Haniotis,
  • Richard C. Russell,
  • Roy A. Hall,
  • Alexander A. Khromykh,
  • Peter D. Kirkland

DOI
https://doi.org/10.3201/eid1805.111720
Journal volume & issue
Vol. 18, no. 5
pp. 792 – 800

Abstract

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To determine the cause of an unprecedented outbreak of encephalitis among horses in New South Wales, Australia, in 2011, we performed genomic sequencing of viruses isolated from affected horses and mosquitoes. Results showed that most of the cases were caused by a variant West Nile virus (WNV) strain, WNVNSW2011, that is most closely related to WNV Kunjin (WNVKUN), the indigenous WNV strain in Australia. Studies in mouse models for WNV pathogenesis showed that WNVNSW2011 is substantially more neuroinvasive than the prototype WNVKUN strain. In WNVNSW2011, this apparent increase in virulence over that of the prototype strain correlated with at least 2 known markers of WNV virulence that are not found in WNVKUN. Additional studies are needed to determine the relationship of the WNVNSW2011 strain to currently and previously circulating WNVKUN strains and to confirm the cause of the increased virulence of this emerging WNV strain.

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