a complex of infections of viral origin, including equine viral rhinopneumonitis (viral abortion), equine viral arteritis, equine influenza and parainfluenza, and equine rhinovirus infection. The diseases are clinically indistinguishable. All cause fever, coughing, and respiratory difficulty; some cause abortion in mares. Treatment includes rest and supportive care. Secondary infections from bacteria, which may create more serious illness, can be prevented by use of drugs.