• WEEV (Western equine encephalitis virus) is a mosquito-borne arbovirus that infects birds and can indirectly transmit to humans and equids, causing severe encephalitic conditions.

• Historically responsible for significant epidemics, WEEV has resurged in Argentina and Uruguay since November 2023. 

• As of April 2024, 103 human and 47 equine cases were reported in South America (Argentina and Uruguay).

• WEEV maintains a natural cycle between birds and mosquitoes, with horses and humans as dead-end hosts. 

• Outbreaks can result from conducive environmental conditions and vector-host interactions.

• America has seen a rise in arboviral diseases, highlighting the changing geographical distribution and frequency of outbreaks.

• Recent increases in malaria, West Nile fever, dengue, and Oropouche virus cases underscore the need for vigilance. 

• Climate change, deforestation, urbanization, and global travel contribute to the spread of arboviruses.

• Understanding vector and host ecology, alongside advanced spatial epidemiology tools, is crucial. 

• Preventive measures within a One Health framework, including vector control, vaccination, and personal protection, are essential for mitigating WEEV's impact.

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