In addition to Henderson County, the disease has been found in Duplin, Forsyth, Mecklenburg, Randolph, Sampson, Surry, Yadkin and Wake counties. Most cases were associated with unsanctioned horse racing. All facilities with infectious horses were placed under quarantine, and remaining horses will be observed and retested in 60 days. 

EIA is an incurable disease commonly spread by biting flies or shared medical equipment between equines, such as horses, mules and donkeys. Clinical signs include fever, weakness, weight loss, anemia, edema and death. However, many infected equine may not show symptoms. All infected equine, including those that are asymptomatic, are carriers of the disease. The disease does not affect people. 

Although the disease is common in other parts of the world, the United States typically has few cases due to regular testing before exhibition or crossing state lines.