The flu strain that has infected at least 1,000 dogs in Chicago likely stems from a canine that traveled from Asia to the United States.

Fox News reports that public health officials initially thought the flu strain in the outbreak was H3N8, but scientists at Cornell University and the University of Wisconsin have now confirmed H3N2 is the main strain.

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It is the first time H3N2 has been identified in North America. The last outbreak of the strain occurred in China and South Korea.

“The H3N2 was brought here almost for certain by a dog from Asia, or that had visited Asia and came over here while they were infective, which is a very short window,” David Gonsky, of West Loop Veterinary Care in Chicago, told Fox News.

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Public health officials are advising local dog owners to refrain from taking their pets to dog parks, day cares, and grooming facilities to help prevent the virus from spreading.

Symptoms of dog flu include coughing, lethargy, fever, and lack of appetite.