Molecular Epidemiology of Western Equine Encephalitis Virus, South America, 2023-2024.
Aline Scarpellini CamposAna Claúdia FrancoFernanda M GodinhoRosana HuffDarlan S CandidoJader da Cruz CardosoXinyi HuaIngra M ClaroPaola MoraisCarolina FranceschinaThales de Lima BermannFranciellen Machado Dos SantosMilena BauermannTainá Machado SelayaranAmanda Pellenz RuivoCristiane SantinJuciane BonellaCarla RodenbuschJosé Carlos FerreiraScott C WeaverVilar Ricardo GewehrGabriel Luz WallauWilliam M de SouzaRichard Steiner SalvatoPublished in: Emerging infectious diseases (2024)
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.