“Equine influenza is the second most common virus in horses, following equine herpesvirus-4,” says Dr. Nicola Pusterla, an internal medicine specialist at the University of California – Davis. “Young horses and older horses are more susceptible,” he says, “And infection would depend a bit on the (virus) strain too. Of horses exposed to the virus, a very high percentage will develop EI.”
Spread mainly through coughing, via respiratory droplets, equine influenza virus can potentially expose large numbers of nearby horses.
Source: The Horse. Link.
The American Association of Equine Practitioners includes equine influenza as a risk-based vaccine, which means veterinarians include it in a vaccination program after the performance of a risk-benefit analysis.
Also see: Research suggests equine influenza virus is zoonotic, Animal Health Digest, April 18, 2018. Link.
INSIGHTS: Equine influenza is primarily an economic disease that affects horse activity, veterinary treatment expenses and the likelihood that infected horses will be removed from competition or daily work.