Veterinary Public Health

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Veterinary Public Health Program
313 N Figueroa St. Rm 1127
Los Angeles, CA 90012
Tel (213) 288-7060
Fax (213) 481-2375
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Canine Influenza
What is Canine Influenza?
Canine influenza (CIV) is a disease in dogs caused by an influenza virus. There are two influenza virus strains that can spread between dogs: H3N8 and H3N2. Both of them cause similar symptoms in dogs. Neither of them are known to make people sick.

The H3N8 virus
was first reported in Florida in 2004. It jumped species from horses to dogs. It has caused a few outbreaks in Los Angeles County (see below). Infected dogs can shed the virus for 2 days before the start of symptoms, and for 4-10 day after. There are vaccines available to help protect dogs from getting sick with this virus.

The H3N2 virus
was first reported in South Korea in 2006, and  the virus caused a large outbreak in the Chicago area in 2015. It likely jumped species from birds to dogs in Asia. It is able to infect cats, although this appears to be rare. Infected dogs shed the virus for 2 days before the start of symptoms, and some may remain contagious for 30 days or more afterward. This virus was first detected in California (in Orange County)in March 2015 and in Los Angeles County in July 2015. Vaccines to protect pets from this virus first became available in November 2015. Reports of this virus causing illness and outbreaks in dogs in Los Angeles County have occurred in 2017, 2018 and 2021.  In 2017, an outbreak of CIV H3N2 affected 35 dogs.  In July 2021, the largest outbreak of CIV H3N2 in Los Angeles County began and is still currently being investigated and managed.


What are the Symptoms of Canine Influenza in dogs?

  • Fever

  • Lethargy

  • Cough

  • Loss of appetite

  • Sneeze

  • Some dogs have no symptoms

  • Nasal discharge


More severe and fatal cases of pneumonia resulting from infection with either strain canine influenza virus have been reported in dogs, but are rare. Most dogs with canine influenza recover in 2-3 weeks.



How does the virus spread from an infected dog to other dogs?

Canine influenza is spread through direct contact with respiratory secretions from infected dogs, and by contact with contaminated objects. The virus is most likely to spread when an infected dog spends time close to other dogs, especially in indoor areas with little ventilation. The virus can survive for 1-2 days on floors or cages.



What Owners Can Do to Protect Their Pet’s Health:
 Some standard recommendations to help prevent spread of disease between pets include:

  • Vaccinate dogs for Canine Influenza H3N2 before they enter boarding kennels, dog day care, dog parks, or engage in dog group activities.  This vaccination is also advisable for dogs that may occasionally encounter other dogs. Canine Influenza and Leptospirosis Vaccine Providers in Los Angeles County and Neighboring Counties 12.6.21

  • Take your pet to your veterinarian if he/she is sick

  • Do not take your dog to public areas if he/she is sick

  • Wash your hands after handling pets - avoid spreading disease between pets

Reporting cases. Veterinarians should report cases using the LA County Canine Influenza Case Reporting Form.Email in to or fax to 213-481-2375. 


Additional Resources:

Canine Influenza H3N2 FAQ  English  Spanish
American Veterinary Medical Association - Canine Influenza Pet Owner's Guide
American Veterinary Medical Association - Canine Influenza FAQs

Last updated: July 19, 2022

Canine Influenza H3N2 in LA County



  • Read more about the outbreak of canine influenza H3N2 in Los Angeles County here

  • From July 2021 to January 2022, a total of 1344 reports of CIV H3N2 cases in dogs in LA County were received by Veterinary Public Health

  • This was the largest outbreak of CIV H3N2 reported in LA County

  • Of the cases reported with known exposure, 85% (972/1146) were associated with attending boarding kennels, dog daycare settings, or shelters.

  • Sadly, 21 deaths were associated with this outbreak.

  • The virus spread rapidly among dogs throughout LA County, affecting at least 68 congregate facilities and 2 animal shelters.  Each facility was contacted, either in person or via phone and email, and given recommendations on how to control the spread. 

  • 15% of the reported cases never visited a boarding or daycare facility but were exposed in settings including walks in their neighborhoods, dog parks, groomers, and veterinary clinics.

  • To stop the spread of the outbreak, pet owners and veterinarians were strongly encouraged to vaccinate dogs against CIV H3N2 and to isolate sick pets at home for 28 days from the first day of illness.  Pets exposed to confirmed or suspected cases were advised to be kept quarantined at home and observed for clinical signs for 14 days. 



  • In late January 2018, a dog in the South Bay area became ill with cough, fever and loss of appetite. The dog tested PCR positive for canine influenza H3N2 by PCR. The source of the infection is unknown - no evidence of an outbreak was found.

  • In mid-March 2018, a group of 3 dogs were imported from South Korea. One of the 3 had ocular and nasal discharge, and tested PCR positive for canine influenza H3N2. The sick dog was placed into 40 days of home isolation, and the 2 exposed dogs were placed in a 14 day home quarantine. An additional dog on the same flight was also quarantined at home for possible exposure.



In 2017, five incidents involving dogs infected with H3N2 were reported. 

  • In March 2017, a small group of ill dogs imported from Asia triggered an outbreak. A total of 35 dogs became ill, and 62 dogs were placed under isolation or quarantine in 17 locations to control the outbreak. Six of the cases were confirmed by PCR testing. The outbreak was successfully contained by isolating sick dogs at home for a minimum of 3 weeks, and then re-testing many of them for the virus. Exposed dogs were quarantined at home for 7 days.

  • In March 2017, a dog developed pneumonia in San Bernardino County and was taken to Los Angeles County for testing and treatment. The dog recovered, and was in isolation for 2 weeks before being placed with a group of 90 other dogs. Since dogs with canine influenza H3N2 can be contagious for more than 2 weeks, an extensive investigation was performed, which determined that the virus had not spread further.

  • In May 2017, a single dog imported from Asia was found to have fever and pneumonia soon after arrival. The dog was taken to two veterinary practices in the San Gabriel Valley area of Los Angeles County. It was kept at home until it appeared healthy, but was not isolated for 40 days. This case was not reported until August 2017.

  • In late July 2017, a dog came home from a boarding facility in the San Gabriel Valley area with a cough. A local veterinarian tested it for influenza by PCR, and it was positive for canine influenza H3N2.  At least 26 other dogs developed coughing during this outbreak. No direct link was found with the single case in May imported from Asia. This outbreak was successfully contained by isolating sick dogs at home for 40 days, and quarantining exposed dogs for 14 days.

  • In early November 2017, a veterinarian in he San Fernando Valley area reported that a dog with moderate coughing had tested positive for canine influenza H3N2 by PCR. The dog had been at a grooming facility during the week before illness, but had no other reported contact with dogs. The dog was placed in home isolation for 40 days, and an investigation was performed. As of November 9, 2017, there was no evidence of an outbreak.


In early July 2015, an adult Labrador mix dog was diagnosed with the new strain of canine influenza H3N2 (i.e. ‘new’ dog flu) in the southern half of Los Angeles County. This was the first confirmed case of canine influenza H3N2 in Los Angeles County.  The dog had stayed in a kennel for about a week, and began coughing the day after it arrived home. It had not visited any other dog parks or other facilities. The dog stayed isolated at home for 3 weeks after becoming ill. Three other dogs developed coughing or sneezing after visiting the facility around the same time period, but all three tested negative for canine influenza viruses by PCR testing.

Last updated March 11, 2022

Canine Influenza H3N8 in LA County


In June 2011, a report was received about four puppies that tested positive for Canine Influenza by PCR in the South Bay Area. The puppies originally were turned in to a local animal shelter, where they were vaccinated against canine influenza (killed virus), in addition to Distemper, Hepatitis, Leptospirosis, Parainfluenza, Parvovirus (DHLPP) and Bordetella. They were emaciated and tested positive for Demodex mange. The puppies were then taken by a rescue group and treated at a local veterinary hospital. They had slight fevers when first examined, and developed a slight cough a week after entering the hospital. PCR testing for canine influenza was performed on pharyngeal and conjunctival swabs collected on the first day of coughing. Their illness was mild and recovery was seen within days. It remains unclear where the four puppies contracted the infection. There was no indication of a larger outbreak at the clinic.



In July  2007, a veterinary clinic in the San Gabriel Valley reported a cluster of respiratory disease associated with the dog boarding section of their facility.  A total of approximately 40 dogs became ill over a period of 3 weeks.  Exposure to canine influenza was confirmed by serologic testing in 5 of the cases. Vigorous infection control measures were implemented to control the outbreak. Most of the dogs had mild symptoms, although four dogs developed  pneumonia.  This outbreak appeared to be triggered after a puppy from Colorado, sick with pneumonia, was brought into the clinic. The canine influenza vaccine was not available in 2007, so none of the dogs had been vaccinated.



In September 2005, an Inglewood veterinarian confirmed four cases among dogs that had been at a single boarding facility at various times during August of that year. Veterinary Public Health conducted extensive surveillance for 6 months following that outbreak, but did not detect additional cases.


Last updated January 26, 2016

Public Health has made reasonable efforts to provide accurate translation. However, no computerized translation is perfect and is not intended to replace traditional translation methods. If questions arise concerning the accuracy of the information, please refer to the English edition of the website, which is the official version.
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