Equine Influenza Virus Disease Guidelines

Equine influenza virus (EIV) is an RNA virus endemic to equine populations in many countries worldwide. Equine influenza outbreaks may also occur sporadically in epidemic form. Countries historically free of equine influenza include Iceland and New Zealand. While epidemic outbreaks have occurred in Australia, Japan, and South Africa, these countries are currently considered equine influenza-free.

Clinical signs vary in their severity depending on the age and immune status of the horse, and asymptomatic infection is possible. Clinical signs are more common and often more severe in younger horses (ages 1-5yo). Older horses generally have milder disease. Equine influenza may be more severe in donkeys and mules.