Background: This is the first EHV-1 outbreak with EHM in Chile. Objectives: Describe clinical, epidemiological and outcome data from an EHM outbreak in South America. Study design: Case Report, retrospective outbreak data analysis. Methods: Clinical and diagnostic data were analyzed. EHV-1 was detected by qPCR (EHV-1-Glycoprotein-B). Frequency tables were used for descriptive analysis of categorical variables and the chi-square test and Cramer’s V to test relationships between them. Results: A total of 567 Polo Horses were kept in the Polo operation, 58.4% were mares and 41.6% geldings and stallions. Mean age was 9.7±0.132 years. 13 horses showed clinical signs compatible with EHV-1 infection, 8 had fever (1.4%) and 11 developed EHM (1.9%). Only 6/11 horses developed EHM and high fevers (>39.5C). The mortality rate was 0.35% (index case and case 1) while morbidity 3.35% (19/567 horses). PCR analysis was performed in 214 horses (37.7%), 201 were negative for EHV-1 (93.9%) and 13 positive (6.1%). 7 horses with a positive PCR presented clinical signs (53.8%), while 6 with a negative PCR result did show clinical signs compatible with EHV-1 infection (2.9%). CT values of positive PCR results ranged from 30 to 39. Main limitations: Limited number of horses were diagnostically analyzed (PCR and/or serology analysis). Viral isolation and sequencing have not yet been achieved. Conclusions: This is the first EHM outbreak reported in Chile showing low morbidity and mortality rates. Viral spread was successfully controlled with prompt and strict quarantine and biosecurity measures. More information on viral prevalence and type during the outbreak and in the Chilean horse population is required to further understand the outbreak and prepare for the impact of future ones.