Norma and Harvey Sheer checked their two pet English springer spaniels into a kennel they had used for years before they left for vacation earlier this month.

The West Nyack couple were shocked when they returned home Thursday to find that the kennel, Best Friends in Chestnut Ridge, had called their son while they were away to pick up the two dogs because of an outbreak of a mysterious illness in the facility.

"Sure enough, as soon as we got them home from the pet sitter last night, they started coughing," Harvey Sheer said yesterday.

He took the dogs, Lilly and Lizzie, to their veterinarian yesterday morning and was told that both animals showed signs of canine influenza, a new and potentially deadly virus diagnosed in dogs throughout the region.

"It´s very unnerving," Sheer said. "You don磘 expect something like this to happen. I just pray that we caught it in time."

It´s unclear how widespread the virus is. More than 100 cases have been reported at Best Friends in Chestnut Ridge. As many as 40 dogs that boarded at Graceland Kennels in North Castle also have come down with the illness, owner Bob Gatti said.

Animal care professionals were told earlier this month there was "reason to believe that canine influenza virus is now present in the New York City area," according to a letter from David W. Chico, a veterinarian with the state Department of Agriculture and Markets.

"Reports have been received indicating an unusual form of 磌ennel cough?has been seen in a number of veterinary practices," the letter said.

Tests done on dogs with symptoms of the illness showed they had a form of canine influenza, according to the state. The illness starts mimicking the common kennel cough. Many animals go on to develop pneumonia, a serious and sometimes deadly complication.

Dr. Cynda Crawford, a veterinarian at the University of Florida College of Veterinary Medicine, sent out an advisory Aug. 12 warning that "outbreaks of canine influenza virus, which causes an acute respiratory infection, have been identified in dogs in shelters, humane societies, boarding facilities and veterinary clinics in Florida."

The illness was first noted in Florida greyhound kennels two or three years ago, according to Dr. Edward Dubovi, director of virology at Cornell University´s Animal Health Diagnostic Center.

The influenza appears to be similar to a type normally found in horses, according to Dubovi.

"From a public-health standpoint, it´s always an alarming occurrence when a virus leaps to another species, particularly into a domesticated species, as this is generally a sign of the virus?strength and ability to adapt," Dubovi said in a statement released yesterday.

Local veterinarians and animal facilities were caught off guard when the virus began showing up in the New York area.

"It´s a new and highly contagious pathogen in dogs," said Debra Bennetts, spokeswoman for Best Friends, a chain of kennels headquartered in Norwalk, Conn.

Dogs can be exposed to the virus at kennels, dog runs, grooming facilities or any other place where they come into contract with other dogs, she said.

Workers at the company´s Chestnut Ridge kennel started noticing just before Labor Day that an unusually large number of dogs were coughing, Bennetts said. A veterinarian treated those dogs for kennel cough, also called canine cough or parainfluenza, and they seemed to get better.

But on Sept. 8 workers were told that one of the dogs came down with pneumonia. Over the next several days, the kennel learned of more dogs that had boarded there and had developed serious illness.

"At that point, we realized we were dealing with something beyond normal parainfluenza," Bennetts said.

Owners of dogs boarding there were notified and asked to pick up the animals as soon as possible. The kennel is closed so workers can disinfect it top to bottom, Bennetts said.

The company, which also operates Best Friends White Plains and Balmoral Kennel in Harrison, sent out letters to more than 100 veterinarians in Westchester, Rockland and northern New Jersey warning them about the illness. No cases have been reported in the company´s other kennels.

Most dogs that have contracted the flu have recovered, Bennetts said. But at least one animal that boarded in Chestnut Ridge died.

Gatti said that workers in his North Castle kennel first noticed dogs were getting sick in July. None of the cases was fatal, he said.

The facility closed its three kennel buildings and completely disinfected them, Gatti said in a letter to customers.

The Oradell Animal Hospital in Paramus, N.J., not far from Chestnut Ridge, has treated 15 dogs for the condition and has had one fatality, according to a letter the facility sent to other veterinarians last week.

Veterinarians are prescribing antibiotics to treat secondary bacterial infections that seem to develop with the virus, said Dr. Russell Petro of Valley Cottage Animal Hospital, who is treating the Sheers?dogs.

Owners of sick pets say they are worried because there seems to be little information about the disease.

"We left our girls at the kennel, and they were fine," Norma Sheer said, referring to her dogs. "Then we come home, and we find out about this disease that no one ever heard of. It´s very upsetting."