An uptick in reports of canine influenza cases in the northeastern United States and Texas has captured the attention of media during what has been so far a quiet flu season in people.

The extent of the “outbreaks” and whether widespread public concern is warranted is unclear, because no central agency or institution monitors influenza in dogs. The virus doesn’t cause illness in humans and generally is not considered serious in otherwise healthy dogs unless it leads to secondary infection.

News outlets including the Wall Street Journal and WCVB-TV in Boston reported this week cases in New York, New Jersey, Connecticut, Massachusetts, Colorado and Texas.

Dr. Edward Dubovi, director of the virology laboratory at the Cornell University College of Veterinary Medicine Animal Health Diagnostic Center, confirmed that he’s seen a spike in positive canine influenza test results on samples taken from dogs in New York City and environs: southern New York, Long Island, northern New Jersey and southern Connecticut.

While his laboratory has seen a distinct increase in positive results, Dubovi said that doesn’t necessarily mean dog flu is circulating more vigorously in greater New York City than before. Dubovi said that New York, as well as Colorado, are enzootic for dog flu, meaning the virus appears in those regions regularly.

“Our data says it’s more this year (in New York) than in a while, but we may not have gotten samples last year,” Dubovi said.

He did not have precise figures on how many positive cases the Cornell lab has detected recently but said the total is several dozen, compared with fewer than five in 2010.

Dubovi noted that the increased detection might be the result of heightened awareness and vigilance rather than a real rise in infections. Because no central database exists for canine influenza, information on national disease incidence often is “done off rumor,” he said.

As for activity outside the New York City area, Dubovi said his lab confirmed cases in several dogs from a kennel in the vicinity of San Antonio, Texas, six to eight weeks ago. He did not know whether the outbreak had spread beyond the single kennel.

Dr. Alice Wolf, a professor emerita at Texas A&M University and a specialist in small-animal internal medicine with an interest in infectious disease, said she, too, had not heard of additional recent cases.

News reports of spreading canine influenza in Texas are circulating nonetheless. An NBC-affiliated news website covering Dallas and Fort Worth reported Wednesday that a local veterinarian, citing cases in the region, is requiring her clients to have their dogs vaccinated. The veterinarian, Dr. Karen Spikes, did not return a call today from the VIN News Service.

As for Massachusetts, the VIN News Service was unable to obtain information about dog flu cases in that state.

Dr. Gabriele Landolt, a researcher at Colorado State University studying the prevalence of canine influenza virus in dogs at shelters in California, Colorado, Florida, New York, South Carolina and Texas, said small outbreaks occur periodically in the Colorado shelter, but she has not heard of a surge in cases in the general population. A spokeswoman in the Colorado Department of Agriculture likewise said the state has received no reports of a jump in dog-flu cases.

Among the states in the shelter-population research, which is funded by the Morris Animal Foundation, Landolt said the virus is most prevalent in Colorado and New York.

Across the United States, canine influenza has been documented in 38 states since the virus first was identified in 2004, according to the website www.doginfluenza.com, which is maintained by Merck Animal Health, maker of one of two canine influenza vaccines on the market.

The Wall Street Journal report cited Merck as the source of information that the virus had been detected in Massachusetts, Connecticut, Colorado and Texas and under investigation in California. The VIN News Service was unable today to reach spokespersons from Merck for comment.

Canine flu first was reported among racing greyhounds in Florida. Up to that point, dogs weren’t known to be susceptible to any influenza virus.

Clinical signs of flu in dogs are similar to those in people: runny nose, cough and fever. Without laboratory diagnostics, canine flu is difficult to distinguish from other respiratory infections, Dubovi said.

The availability of the first canine influenza vaccine in 2009 raised questions among veterinarians across the country about the threat of dog flu and the value of immunizing pets against the virus. Interest in the vaccine appeared high among pet owners, probably because a human flu pandemic occurring at the time was caused by a virus that had transmitted from people to a house cat and ferrets.

By contrast, the big flu story at the moment is the reported spike in dog flu; human influenza has been mild so far this season, judging from the latest surveillance report by the U.S. Centers for Disease Control and Prevention.

Boston’s WCVB-TV, in a brief segment on dog flu posted to its website Wednesday, reported that the American Veterinary Medical Association (AVMA) now is recommending the flu vaccine be given to dogs that regularly are boarded, attend day care or travel. But contrary to the report, officials at the AVMA told the VIN News Service today that the association’s position has not changed since 2009, when it deemed the immunization to be a “lifestyle” vaccine not recommended for every dog.

Its statement on the subject advises: “Dog owners should consult with their veterinarian to determine whether their dog’s lifestyle includes risks for exposure to the (canine influenza) virus and if the vaccine is appropriate for their dog.”

In general, veterinary infectious disease and immunization experts recommended the canine influenza shot only for dogs that come into regular contact with other dogs — show dogs and racing dogs in particular, and pets that frequent dog parks or are kept in day care or boarding kennels in areas where outbreaks are occurring.

Wolf, the small-animal internal medicine specialist in Texas, said the advice given to most human patients to receive a flu shot annually does not apply to dogs because they usually do not mingle with other dogs to the extent that people mix with other people.

“Most dogs I know do not travel extensively in the company of hundreds of other dogs from all over the U.S. nor work eight hours a day in a closed environment with hundreds of other dogs from all over a local area,” Wolf said. “Few ride buses with other dogs, go to school or work in hospitals.”