EQUINE herpes virus is a common virus that occurs in horse populations worldwide. The two most common strains are EHV-1 which causes abortion, respiratory disease and paralysis and EHV-4 which usually causes respiratory disease only but can occasionally cause abortion.

A maiden filly arrived to the National Stud in Newmarket, from France, on January 20th and was found to have an EHV-1 infection. The virus was found in the filly while she was stabled at the isolation unit, which is one mile from the main stud.