I have recently received many questions regarding the canine influenza (“dog flu”) virus and vaccine. Canine influenza is a relatively newly identified disease. Various outbreaks have occurred in the US since 2004.

Two strains of the canine influenza virus exist. The H3N8 strain broke out in Florida in 2004, and has caused sporadic outbreaks since then. The H3N2 strain is a newer form of the virus, and it generally causes more mild disease than does H3N8. H3N2 was first identified in Chicago in 2015. In May of this year, it was diagnosed in dogs in several midwestern and southeastern states, including North Carolina and South Carolina.

Most cases of canine influenza are not fatal. Most affected dogs will have the mild form of disease, which may cause lethargy, coughing, fever, and decreased appetite. Sneezing and discharge from the eyes or nose may be noted.

The disease may also occur in a less common but more severe form, characterized by a high fever and pneumonia. Pneumonia is usually the result of secondary bacterial infection due to the dog’s natural defenses being weakened by the flu virus. Pneumonia may cause death in very severe cases, or in cases that are left untreated. Very old or very young dogs are more likely to suffer from the severe form of disease.

Transmission of the flu virus usually occurs from direct contact with an infected dog. The virus is most contagious before the affected dog is showing any symptoms. Therefore, seemingly healthy dogs may transmit the virus before anyone knows they are ill.

If canine influenza has been reported in your area, dog owners are advised to monitor their dogs closely for any signs of coughing and fever. If these signs are noted, affected dogs should be examined by a veterinarian.

Affected dogs should be separated from other dogs until the virus has run its course. Diagnosis may be confirmed with a blood test. Treatment is mainly supportive and is addressed at managing specific symptoms of disease. If pneumonia is suspected, chest x-rays and oxygen therapy may be recommended.

Three different types of vaccines are available to help prevent canine influenza. There is a vaccine for the H3N8 strain, one for the H3N2 strain, and a new bivalent vaccine that covers both strains. At this time, the bivalent vaccine is generally preferred.

Dogs that go to dog shows or agility trials, and those that are boarded frequently, are the most at-risk for canine influenza. If you believe your dog is at risk, please discuss the canine influenza vaccine with your veterinarian.

The vaccine must be given initially, then boostered in three weeks. The vaccinated dog is not considered protected until one week after the second booster has been administered. Therefore, it takes about one month from the initial vaccine until the vaccinated dog is protected.

Not all dogs are at risk for canine influenza, but those that are should have the flu vaccine. Tammy and Twyla, my clinic Chihuahuas, have already had theirs!