Surprisingly, dogs can be sick for up to three weeks. In about 90 percent of cases the symptoms are mild, but 10 percent of cases can be severe or progress to pneumonia or death.
The disease has spread with surprising swiftness.
"It was in south San Jose one week and the next week it was on our doorstep," said Dr. Janet Lowery, co-owner of Mid-Peninsula Animal Hospital in Menlo Park. Her hospital has had four to five confirmed cases through DNA testing, she said.
The disease is concerning because both strains are new in dogs, who have no immunity against them, she said.
The H3N8 virus originated in horses and has been known to infect them for at least 40 years, according to the U.S. Centers for Disease Control and Prevention. In 2004, it mutated and jumped to dogs, initially infecting greyhounds. Scientists believe it spread among dogs in kennels and shelters.
The canine H3N2 virus, which is currently the most prevalent in the Bay Area, initially infected birds and was first detected in dogs in South Korea, China and Thailand in 2007, according to the CDC. An outbreak in Chicago in April 2015 sickened more than 1,000 dogs and killed five.
Many local dog owners are heeding veterinarians' warnings to get their pets vaccinated and to refrain from frequenting dog parks, groomers, and day-care and boarding facilities until the pet has received the two-part vaccination and its body has created immunity — in all, a period of more than a month.
But staying away from shared spaces can be difficult for some owners and pets.
"If we stayed home that long, we'd all go crazy," dog owner Suzanne Attenborough said at Mitchell Park on Tuesday. On the warm, sunny afternoon, canines shared saliva-covered balls and water dishes and romped together on the grass. Attenborough's dogs, 6-year-old Wendell, a mellow golden retriever, and Kimberly, an 8-year-old white Labrador retriever, had only had their first shots.
Cheyenne, a 2 1/2-year-old yellow Labrador retriever, chased one of the dozen soggy tennis balls strewn around the play area. His owner, Mary Ann Cusenza, said he has had his shots, but he has not completed the entire waiting period.
"I was quite worried about it," Cusenza said of the flu.
Still, she weighed the risk of not waiting out the last two weeks after the booster shot versus not exercising or socializing her pet. She and the other dog owners said they feel fairly safe at the Mitchell Park dog run because they all know each other, and everyone is responsible about not bringing sick pets to the park.
Still, dog flu concerns are putting a damper on play time.
"It's a gorgeous day and at 4:30, it's prime time, but it's underpopulated here. We have six dogs here; normally we have 25 to 30," said Jo Ann Mandinach, who was at the park with her frisky black poodle, 11-year-old Rico.
Mandinach said she hasn't taken Rico for his flu vaccinations despite the warnings. She doesn't get a flu shot for herself and doesn't get the flu. Her partner, who does get the shot, still gets sick. Rico is a healthy dog despite his age, so she isn't concerned that he would become very ill if he did catch the virus.
But veterinarians said the virus can spread when dogs sniff each other, nuzzle, lick or share water, food and toys — even when dogs seem healthy.
"Canine influenza has some of the highest degree of virus shedding prior to when dogs show symptoms. The fact that they can be contagious prior to showing clinical symptoms is a bit scary," Mid-Peninsula Animal Hospital's Lowery said.
Humans can spread the disease to pets if they have come in contact with a dog who has the illness. Dog flu can contaminate clothing, shoes and other objects. The virus stays live for 24 to 48 hours.
The disease is significantly affecting veterinary clinics and hospitals, where veterinarians and staff must wear surgical caps, gowns, booties and gloves. Each time they see a new pet, the doctor and staff must discard the paper coverings and disinfect the exam room with bleach, Lowery said.
Pet clinics are being inundated with calls and are busy with vaccination appointments.
Mid-Peninsula has so far held five vaccination clinics, and they are booked for every 10 minutes, she said.
Dr. Brennen McKenzie, a veterinarian at Adobe Animal Hospital in Los Altos, said the hospital's Los Gatos office has had drive-by vaccine clinics where pets are met and examined in the client's vehicle before given an injection.
At the Los Altos office, dogs won't get in the door without a parking-lot exam. Sick animals can be treated in an isolated room or housed in a quarantined area if they are hospitalized, he said.
Adobe Hospital has confirmed 13 cases with lab tests.
"But there are more we think that are unconfirmed because their owners have declined to have the lab tests done. I know for sure of four cases that have required hospitalization, with some having pneumonia. They are mostly older dogs and puppies," he said.
Alpine Animal Hospital in Mountain View has also seen cases, some of which have been confirmed by testing and others in which owners declined to do lab tests.
"We've had quite a few cases coming in but no fatalities," manager Stephanie Zeman said.
Tammy Steely, practice manager at Animal Hospital of Palo Alto, said the hospital has not had any cases of dog flu. But they have had an overwhelming number of calls from concerned dog owners — more than 15 per day since the outbreak.
Worries over dog flu have affected other dog-related services. Animal Hospital of Palo Alto has a boarding facility, which has seen a decline in bookings since the outbreak, Steely said. No dogs are allowed unless they have had all of the injections.
Ashley Erens, assistant manager at dog day care facility A Dog's Life in Palo Alto, said they have at least five cancellations each day.
"They are not coming in until the dogs have had both rounds of the shots," she said.
A case confirmed Tuesday illustrates the need for vigilance, she noted. A dog had visited the facility after having its first shot, but he still came down with influenza. He was two days from receiving the booster, she said.
"We have been cleaning every minute of the day with bleach and other cleaning supplies. We have been dousing the whole facility since early to mid-January," she said. "We've emailed all of the parents so they can be hyper-vigilant, and we've deep cleaned the one room where that dog was."
Dog grooming facilities are also seeing some deferred business.
"No two ways about it. In the last couple of weeks we have had some cancellations," said groomer Carol O'Connell of Alexander's Grooming Salon in Palo Alto.
"We haven't had any instances of dog flu. We can only hope people are honest and realistic with their dogs," she said. "We are hoping it will come and go very quickly. We are using lots of disinfectant."
O'Connell said the last communicable dog disease she saw to rival canine influenza was decades ago when canine parvovirus broke out.
Parvovirus appeared in 1978, causing a widespread epidemic in dogs of all ages because, like canine influenza, it was a new virus that no dogs had been exposed to before, according to the Cornell University College of Veterinary Medicine.
Most flu viruses are species-specific and therefore aren't a threat to other animals or humans, veterinarians said. But H3N2 dog flu virus has been reported to infect cats, which so far have developed mild symptoms. There isn't a vaccine for felines, however.
According to the U.S. Centers for Disease Control, because the influenza virus constantly mutates, it is possible canine influenza could change to infect humans, although that is not the case now. Human infections with new influenza viruses (such as avian and swine flu), against which the human population has little immunity, are concerning, the CDC noted. They could create a pandemic, so the CDC is monitoring both canine influenza viruses and other animal influenza closely. But researchers think dog flu poses a low threat to people, according to the CDC.
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