A highly contagious illness is affecting dogs and perplexing veterinarians in Colorado.
What to know: The persistent respiratory disease includes coughing, sneezing and lethargy — with cases evolving into serious pneumonia that is hospitalizing man's best friend.
Why it matters: The cases are most prevalent in Colorado, Oregon and New Hampshire, the Associated Press reports.
The big picture: The U.S. Department of Agriculture's National Veterinary Services Laboratory is working to determine the cause of the illnesses.
Of note: This is not kennel cough, which typically lasts seven to 10 days and is easily treatable.
Be smart: If pet owners notice symptoms, they are instructed to contact their veterinarian as soon as possible.