Emerging Infectious Diseases (Sep 2024)

Molecular Epidemiology of Western Equine Encephalitis Virus, South America, 2023–2024

  • Aline Scarpellini Campos,
  • Ana Claúdia Franco,
  • Fernanda M. Godinho,
  • Rosana Huff,
  • Darlan S. Candido,
  • Jader da Cruz Cardoso,
  • Xinyi Hua,
  • Ingra M. Claro,
  • Paola Morais,
  • Carolina Franceschina,
  • Thales de Lima Bermann,
  • Franciellen Machado dos Santos,
  • Milena Bauermann,
  • Tainá Machado Selayaran,
  • Amanda Pellenz Ruivo,
  • Cristiane Santin,
  • Juciane Bonella,
  • Carla Rodenbusch,
  • José Carlos Ferreira,
  • Scott C. Weaver,
  • Vilar Ricardo Gewehr,
  • Gabriel Luz Wallau,
  • William M. de Souza,
  • Richard Steiner Salvato

DOI
https://doi.org/10.3201/eid3009.240530
Journal volume & issue
Vol. 30, no. 9
pp. 1834 – 1840

Abstract

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Western equine encephalitis virus (WEEV) is a mosquitoborne virus that reemerged in December 2023 in Argentina and Uruguay, causing a major outbreak. We investigated the outbreak using epidemiologic, entomological, and genomic analyses, focusing on WEEV circulation near the Argentina‒Uruguay border in Rio Grande do Sul state, Brazil. During November 2023‒April 2024, the outbreak in Argentina and Uruguay resulted in 217 human cases, 12 of which were fatal, and 2,548 equine cases. We determined cases on the basis of laboratory and clinical epidemiologic criteria. We characterized 3 fatal equine cases caused by a novel WEEV lineage identified through a nearly complete coding sequence analysis, which we propose as lineage C. Our findings highlight the importance of continued surveillance and equine vaccination to control future WEEV outbreaks in South America.

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