Although the Equine Coronavirus has been known to cause diarrhoea in foals for decades, it has increasingly been detected in adult horses (>2 years) in recent years. In this age group, the focus is mainly on febrile diseases, rarely accompanied by gastrointestinal symptoms such as diarrhoea or colic. Recent years show a large proportion of infections with ECoV are subclinical or can result in asymptomatic shedding of the virus. Due to new findings in recent years, ECoV should be considered as a differential diagnosis not only in foals but also in adult horses showing fever of unknown origin with or without gastrointestinal symptoms. This web seminar illuminates the medical approach such as clinical examination and the correct laboratory diagnostics in a patient presented with high fever as main symptom and gives some background information about the Equine Coronavirus and its differential diagnoses.