RALEIGH, N.C. (WNCN) — Infectious anemia in horses appears to be spreading in North Carolina with 19 cases across nearly 10 different counties, the N.C. Department of Agriculture said Friday.

Of the 19 infected, 17 of the horses have been euthanized.

Most of the active cases are associated with “unsanctioned horse racing,” officials said in a news release Friday.

The disease is incurable and is commonly spread by biting flies or shared medical equipment between equines, such as horses, mules and donkeys.

The disease has been found in Wake, Duplin and Sampson counties in central North Carolina, officials said Friday.

“All facilities where infectious horses were discovered are placed under quarantine, which restricts movement of equine,” said Dr. Catherine Harris, director of Livestock Health Programs.

The disease was discovered most recently this past November through a collaboration by private veterinarians, N.C. Department of Agriculture Veterinary Division field staff, the N.C. Veterinary Diagnostic Laboratory in Raleigh and the U.S. Department of Agriculture.

The disease was also found this week in Forsyth, Henderson, Mecklenburg, Randolph, Surry and Yadkin counties, according to the news release.

Clinical signs of EIA include fever, weakness, weight loss, anemia, edema and death. However, many infected horses may not show symptoms. All infected horses, including those that are asymptomatic, are carriers of the disease. The disease does not affect people.