Equine influenza has spread to nearly 20 premises—mostly Thoroughbred training stables–in the United Kingdom, and it has been detected in the eastern, central, and southern parts of the country. “The reason(it’s unusual) is because despite the fact that horses have been very well vaccinated and have very high antibody levels, they are still becoming infected with this strain of virus,” according to James Wood, BSc, BvetMed, MSc, PhD, MRCVS, DLSHTM, Dipl. ECVPH, head of epidemiology at the Animal Health Trust in the United Kingdom.
He said no racetracks have been affected by the illness.

Influenza, while typically not life-threatening, can make a horse uncomfortable and vulnerable to other diseases. Infected horses usually require a minimum of three to four weeks of rest to avoid long-term respiratory problems. Affected horses spread the virus via aerosol droplets or fomites (any objects capable of mechanically transporting an infectious agent, such as brushes or buckets). Horses exposed to transient populations, those stressed by shipping or heavy training schedules, young horses, and seniors are most at risk of contracting influenza. Signs in the current outbreak have included acute coughing, mainly during exercise, and some horses have developed nasal discharge. Fever has been seen, but is not a consistent sign