Equine encephalitides are a group of viral diseases transmitted to humans by arthropods. Eastern equine encephalitis (EEE), Western equine encephalitis (WEE) and Venezuelan equine encephalitis (VEE) are considered the most important for their distribution and impact on public health in the Americas.The etiologic agent of these viral diseases belongs to the genus Alphavirus, family Togaviridae.

On 19 March 2010, the Ministry of Health of Argentina reported the occurrence of two confirmed cases of Saint Louis Encephalitis (SLE) infection in the nation's capital city of Buenos Aires. The SLE virus has caused outbreaks in the central part of the country (mainly in the provinces of Córdoba and Entre Ríos), and this is the first time that it has been detected in Buenos Aires. This virus has epidemic potential.

The Ministry of Health of Argentina had confirmed new cases of Saint Louis Encephalitis (SLE) virus infection. Until 29 March 2010, it has been reported four confirmed cases of SLE infection in the nation's capital city and in Buenos Aires province. The SLE virus had previously caused outbreaks in the central part of the country (mainly in the provinces of Córdoba and Entre Ríos), and this is the first time that it has been detected in Buenos Aires.

On February, one case of human VEE was reported to national authorities in Colombia, involving a soldier who had been in the Yondó province (Department of Antioquia).

In the municipality of Arismendi, State of Barinas, two outbreaks of Venezuelan Equine Encephalitis (VEE) and Eastern Equine Encephalitis (EEE) have been detected beginning at the end of September.