Journal of Preventive Medicine & Infectious Diseases

Abstract

Introduction: West Nile fever (WNF) is a mosquito-borne arboviral disease involving birds, equids, humans, and climate- and environment-related factors. This study aimed to describe the epidemiological profile of WNF in the Americas, with emphasis on Brazil, and to discuss the importance of integrated One Health surveillance.

Methods: An observational, descriptive, retrospective epidemiological study was conducted. Animal data reported to the World Organisation for Animal Health from 2015 to 2025 were analysed. Human data were obtained from Technical Note No. 79/2026 issued by the Brazilian Ministry of Health and covered cases recorded in Brazil from 2014 to 2026. Absolute and relative frequencies were calculated by year, six-month period, country, Brazilian federative unit, animal category, and species.

Results: A total of 4,033 animal cases were recorded in the Americas, with peaks in 2018 and 2023 and a renewed increase in 2025. Reports predominated in the second half of the year and among domestic animals, particularly equids. In Brazil, 15 animal cases were identified from 2018 to 2021, mostly in Espírito Santo State. From 2014 to 2026, 17 confirmed and one probable human case were recorded across different Brazilian regions and biomes.

Conclusions: Integrating the surveillance of human cases, equids, wild birds, and mosquito vectors with the monitoring of climatic and environmental conditions is essential to strengthen early detection and response to WNF under a One Health approach.