On Monday, researchers reported that the mysterious disease was an influenza strain that jumped from horses to dogs.
Such a rapid jump into a new species is rare; the flu usually evolves into new strains more gradually.
But genetic tests of sick dogs found their disease almost identical to the H3N8 influenza strain that afflicts horses, scientists at the Centers for Disease Control and Prevention and University of Florida discovered. The results were published online Monday by the journal Science.
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