When they got home their dogs were coughing uncontrollably and showing signs of a new and potentially deadly strain of species-hopping influenza that is terrifying American pet owners.
The dog flu is spreading like wildfire from greyhound tracks to kennels to grooming parlours. Even taking the dog for a walk in the park is a risky activity.
The virus has mutated from a strain of influenza that cripples horses and has killed racing greyhounds in seven states. The illness starts by mimicking the common kennel cough. Many animals develop pneumonia, with sometimes deadly complications.
Cynda Crawford, an immunologist at the University of Florida, says it spreads most easily where dogs are housed together, but it can also be passed on the street, in dog runs or even by a human transferring it from one dog to another. Kennel workers seem to be spreading the virus by carrying it home with them, she said.
Dr Crawford first investigated greyhound deaths at a racetrack in Florida, where eight of the 24 greyhounds who contracted the virus died.
"This is a newly emerging pathogen," she said, "and we have very little information to make predictions about it. But I think the fatality rate is between one and 10 per cent."
The canine flu, for which there is not yet a vaccine, is causing pandemonium among dog owners, who find they can no longer simply drop off the dog with the walker and assume the best.
"I've been telling any client of mine who boards their dog to be very careful," said Russell Katz, a New York vet, who has treated at least five dogs with symptoms of the virus.
Responding to the nerviness of New York pet owners, Dr Katz is telling them that before taking their pets to grooming parlours or dog playgrounds, they should "ask questions of other owners about whether their dogs have been kennelled". But even this level of caution is probably pointless, as dogs do not have any natural immunity to this illness.
"It will be impossible for anyone to have a normal life with a dog and avoid any contact with this virus," Dr Katz told The New York Times, to the dismay of countless dog-owners.
In his own practice, Dr Katz says, any dogs with a cough were made to wait outside the waiting room, or in a far corner of it. They were moved quickly to a treatment area, and any surface they had touched was treated with bleach, to minimise the possibility of contamination.
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 Centre.
"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's strength and ability to adapt," he said.
Owners of sick pets continue to worry: "It's very unnerving," Mr Sheer told his New Jersey newspaper The Journal News. "You don't expect something like this to happen. I just pray that we caught it in time."