A mysterious disease is spreading among dogs in the United States with over 10 states affected, media reports said.

CBS reports that hundreds of pets are getting sick due to this lethal respiratory illness.

The Oregon Department of Agriculture, in a recent statement, labelled the mysterious sickness as an "atypical canine infectious respiratory disease."

In Oregon, veterinarians have recorded over 200 cases of the disease since mid-August, and more cases have been reported in states such as Colorado, Illinois, and New Hampshire.

Dogs with the mysterious illness display symptoms like upper respiratory disease, but they test negative for common respiratory infections, according to Dr. David B. Needle, a pathologist at the New Hampshire Veterinary Diagnostic Laboratory and clinical associate professor at the University of New Hampshire.

Deaths are not a prominent feature of the disease being investigated as instances of acute and potentially fatal pneumonia as secondary infections are rare, he said.

Dr. Needle suggests that if the identified pathogen is responsible, it may be host-adapted bacteria with a history of colonizing dogs.

He theorizes that an "evolutionary event" such as a spontaneous mutation or acquisition of a gene from a different source could have made the bacteria virulent.

To keep dogs safe, they should be kept away from sick dogs as well as from contact with large numbers of unknown dogs.

Further, the canines should not be allowed to access communal water bowls

Sick dogs should be kept at home and provided with veterinary care.