Every inch the pampered purebred, the fluffy white dog Curry stands like a statue for his haircut at the Best Friends Pet Resort and Salon.

He looks, and is, perfectly healthy. But Curry, a bichon frise, was one sick puppy a month ago. And the Best Friends kennel was forced to close for three weeks after more than 100 other dogs began showing signs of what turned out to be a new disease: canine influenza virus, or dog flu.

"He was extremely lethargic, having a hard time breathing," said Curry's owner, Margaret Ragi of Upper Saddle River, N.J. "The life just wasn't there in his eyes. We were really worried."

Lots of dog lovers are worried these days. Experts say the flu is spreading steadily through the nation's dogs, with no vaccine available to curb it. Perhaps 5 percent of its victims are dying.

Researchers recently found to their surprise that the virus had crossed over from horses to dogs, striking greyhounds at racetracks in 11 states. Now it has been found in pets, with cases documented in California, Florida, Massachusetts, New Jersey, New York, North Carolina, Ohio, Oregon and Washington state.

"One-hundred percent of dogs will be susceptible," said Edward Dubovi, director of the animal virology lab at Cornell University (search). "I would expect to see this infection moving thorough groups of dogs until a large percentage gets infected and there are a lot of immune dogs."

Cynda Crawford, a veterinary immunologist at the University of Florida, said researchers are getting positive readings on 30 percent to 40 percent of the blood and tissue samples sent in by veterinarians who think they might be treating a dog with influenza. The symptoms include a cough, low-grade fever and a runny nose.

Exactly how many dogs have died is unclear. Crawford said many of the animals were young and otherwise healthy.

Many pet owners and veterinarians have been fooled because some of the symptoms mimic a common, less dangerous bacterial infection known as kennel cough.

As with human influenza, dog flu is most easily contracted in gathering places — kennels, dog shows, animal shelters, even dog runs in parks.

That has resulted in a lot of lonely dogs, as pet owners keep them home to avoid the flu. Several days after the kennel in Chestnut Ridge reopened, there were just six dogs in "doggie day care," down from the usual 17, and just 50 boarding, down from 150, said manager Kelly Kurash.

The suburban New York kennel had closed Sept. 10 after staffers realized that the illness going around was not kennel cough. Dogs were sent home or to hospitals, and one sheepdog died a few days later.

"We knew we were dealing with something more serious," said Deborah Bennetts (search), spokeswoman for the Best Friends chain, based in Norwalk, Conn. "It seemed to be spreading and some dogs were getting seriously ill."

Tests on the dogs confirmed the new virus.

Best Friends had the entire building disinfected and changed the air conditioner filters. When the kennel reopened Sept. 30, some dogs were turned away. At the 42 Best Friends kennels in 18 states, "we're not allowing any dog that has boarded within the last two weeks or has been at a dog show or some kind of group setting like doggie day care," Bennetts said.

Dubovi said researchers are at work on a vaccine, but it could be months before it becomes available.

Some vets fear another upswing in cases at Thanksgiving and Christmas, when, as in the late summer, many people go away and put their dogs in kennels.