Search query Equine herpes outbreak causing event cancellations in Arizona Sat, November 22, 2025 at 4:36 AM UTC Three cases of Equine Herpes Virus have been confirmed in Arizona, according to state agriculture officials. The virus can be deadly to horses because it can affect a horse's respiratory and nervous system functions. To limit the threat, 10 arenas and producers across Arizona decided to pull back the reins on their events.