Colorado dogs getting mysterious illness and cough

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.

• The illness is airborne and transmitted through contact, such as nose-to-nose touching.

Why it matters: The cases are most prevalent in Colorado, Oregon and New Hampshire, the Associated Press reports.

• In some situations, the illness is not responding to antibiotics and dogs have died.

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.

• It's a novel illness, possibly a virus, that is evading dogs' immune systems, especially for puppies.

Be smart: If pet owners notice symptoms, they are instructed to contact their veterinarian as soon as possible.

• Other steps pet owners can take are making sure their dogs get vaccines for canine influenza and Bordetella, and avoid dog parks, day care and boarding facilities, Gina Kettig, a veterinarian at VCA Alameda East Veterinary Hospital, told 9News.