The new canine H3N2 flu virus has now been detected in as many as 13 states, though most cases have been reported near Chicago, where the virus first turned up in the middle of April, according to veterinary groups and lab reports.
The virus is related to an H3N2 strain that has infected dogs in southern China and South Korea since 2006.The US Centers for Disease Control and Prevention (CDC) said in late April that a genetic analysis of the new strain found no sign that it can infect or cause severe disease in humans.
The more common H3N8 canine flu, which has been circulating in the United States since 2004, also poses a low threat to humans.
Virus expands reach
Cornell University Animal Health Diagnostic Center (AHDC) has been monitoring detections nationwide, and its most recent map as of May 6 shows that positive tests for the virus have come from 11 states: California, Texas, Iowa, Illinois, Wisconsin, Indiana, New York, Massachusetts, Rhode Island, Alabama, and Michigan.
Since then, tests in Georgia and possibly in Ohio have detected H3N2 in dogs, which would raise the number of affected states to 13. The University of Georgia Veterinary Diagnostics Laboratories (UGVDL) announced on May 19 that the strain was detected in a dog from the metropolitan Atlanta area that had recently been in contact with other dogs at an Atlanta boarding facility.
Meanwhile, a possible case was detected in the Ohio city of Newark this week, but a second round of tests are needed to confirm the diagnosis, according to a May 20 statement from the Ohio State University (OSU) College of Veterinary Medicine.
Joshua Daniels, DVM, PhD, associate clinical professor in veterinary clinical sciences, said in the statement, "Because this is an emerging disease in a single animal in a new geographic area, it should be confirmed by a secondary test."
Detections outside of Illinois appear to be sporadic. But in the Chicago area, more than 1,700 cases, including 8 known deaths, have been reported, the Chicago Veterinary Medical Association (CVMA) said in a May 18 statement.
Experts urge precautions
Donna Alexander, DVM, director of the Cook County department of animal and rabies control, urged dog owners to remain on heightened alert and said there has been no let-up in the number of severe canine respiratory cases in the Chicago area.
The CVMA said that, because of the high risk of dog-to-dog spread, owners should take precautions and avoid allowing dogs to socialize with other dogs in settings such as training classes, kennels, doggie daycares, dog parks, and grooming facilities until further notice.
The Cornell AHDC, which has been heavily involved in testing samples, said in its background materials that all subtyped samples from the Chicago area have been the new H3N2 strain. Though the virus can be transmitted to cats, no cats have tested positive in the outbreak so far.
Cornell experts said it's not known whether an H3N8 vaccine that is available for dogs offers any protection against the H3N2 strain. They said group settings pose the most risk, and—as for other infectious diseases—extra measures should be taken for puppies, older dogs, and those that have underlying health conditions.
The Cornell group added that especially severe disease has been seen in some groups of greyhounds.
Cornell AHDC canine influenza testing map
Apr 13 CIDRAP News scan "New H3N2 virus implicated in Chicago canine flu outbreak"
Apr 29 CIDRAP News scan "CDC study suggests dog flu virus poses little threat to humans"
May 19 UGVDL statement
May 20 OSU College of Veterinary Medicine press release
May 18 CVMA press release
Cornell AHDC canine influenza virus FAQ
Cornell AHDC H3N2 FAQ