RESUMEN
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 ArgentinaâUruguay border in Rio Grande do Sul state, Brazil. During November 2023âApril 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.
Asunto(s)
Brotes de Enfermedades , Virus de la Encefalitis Equina del Oeste , Epidemiología Molecular , Filogenia , Animales , Virus de la Encefalitis Equina del Oeste/genética , Humanos , Caballos , Uruguay/epidemiología , América del Sur/epidemiología , Enfermedades de los Caballos/epidemiología , Enfermedades de los Caballos/virología , Masculino , Encefalomielitis Equina del Oeste/epidemiología , Encefalomielitis Equina del Oeste/virología , Femenino , Argentina/epidemiología , Encefalomielitis Equina/epidemiología , Encefalomielitis Equina/virología , Encefalomielitis Equina/veterinaria , AdultoRESUMEN
During the ongoing western equine encephalitis virus (WEEV) outbreak in South America, we described three fatal cases in horses from Rio Grande do Sul, Brazil. We sequenced WEEV strains and identified a novel lineage causing these cases. Continued surveillance and horse immunization are needed to mitigate the WEEV burden.