Horses commonly get viral upper respiratory diseases, especially Equine Herpes Virus and influenza. Horses also get many other less familiar viruses (akin to the common colds in humans).

Viral respiratory tract infection is usually brought on by exposure to outside horses (travel to show or new horse in barn) harboring the virus. When viral respiratory disease is suspected, vets often treat symptomatically, assuming that the virus will run its course. Attention is also given to prevent its spread to other horses.

Viruses damage the natural immune function of the respiratory tract, enabling bacteria to establish a foothold. Viruses do not respond to antibiotics, however antibiotics are often used to prevent secondary bacterial infection. However, the practice of treating apparent viral infections with antibiotics has come under more scrutiny as the problem of resistant organisms has worsened.

Good nursing care is important. Monitor the horse to ensure they are still eating, drinking, urinating and defecating normally and that their attitude and appetite are good. Monitor the amount and appearance of nasal discharge, severity of cough and, especially, the horse's general attitude and appetite.