Equine Viral Arteritis (EVA) is an infectious viral disease. It is spread by respiratory and venereal means, through semen at natural service or artificial insemination, and direct contact. Following exposure, signs take 7-10 days to develop and include fever, nasal discharge, and swelling of the head and legs. Stallions can develop swelling of the sheath and scrotum.

The disease itself is not usually very severe and most, otherwise healthy, horses recover with rest. However, it can cause abortion in mares and life-threatening illness in young foals. Symptoms are flu-like and tend to be more severe in older horses and horses in poor condition.

Unlike EHV-1, in which abortion occurs long after other signs of illness have passed, EVA causes abortion at the same time as the other signs. Stallions can be symptomless carriers, spreading the virus in their semen. A mare should be adequately vaccinated before insemination from a carrier stallion. In many areas, breeding stallions are tested for and vaccinated against this disease.

EVA is a reportable disease, meaning that if a horse has or is suspected of having this disease, vets are required to report it to agricultural authorities (usually the State Veterinarian). These authorities may investigate the case as part of a larger effort to monitor equine health and coordinate with other states and the USDA APHIS in preventing the spread of illness or disease on a national and international level.