Currently, two strains of CIV have been identified in the U.S. The
H3N8 strain of canine influenza was first identified in 2004 in Florida. Since
then, it has been found in several other states. In 2015, the H3N2 virus strain
was identified as the cause of an outbreak of canine influenza in Chicago. The
virus was known to exist in Asia, but the 2015 outbreak was the first report of the
H3N2 virus affecting dogs outside of Asia.
Canine influenza can occur year round. So far, there is no
evidence that canine influenza infects people.
In early 2016, a group of cats in an
Indiana shelter were infected with H3N2 canine influenza (passed to them by
infected dogs). The findings suggested that cat-to-cat transmission was
possible. Cats infected with H3N2 canine influenza show symptoms of upper
respiratory illness, including a runny nose, congestion, malaise, lip
smacking and excessive salivation.
The symptoms of a CIV infection resemble those of canine
infectious tracheobronchitis ("kennel cough"). Dogs infected with CIV develop a persistent
cough and may develop a thick nasal discharge and fever (often 104-105oF).
Other signs can include lethargy, eye discharge and reduced appetite. Canine
influenza infections can cause mild to severe illness in dogs. Some infected
dogs may not show any signs of illness, but can still be contagious and able to
infect other dogs
Most dogs recover within 2-3 weeks. However, some dogs may develop
secondary bacterial infections which may lead to more severe illness and
pneumonia. Anyone with concerns about their pet’s health, or whose pet is
showing signs of canine influenza, should contact their veterinarian.
Laboratory tests are available
to diagnose both H3N8 and H3N2 CIV. Consult your veterinarian for more
information regarding testing for CIV.
Dogs infected with CIV are most contagious during the two- to
four- day virus incubation period, when they shed the virus in their nasal
secretions but do not show signs of illness. The virus is highly contagious and
almost all dogs exposed to CIV will become infected. The majority (80%) of
infected dogs develop flu-like illness. The mortality (death) rate from CIV is
low (less than 10%).
To reduce the spread of CIV, isolate dogs that are sick or showing
signs of a respiratory illness, and isolate dogs known to have been exposed to
an infected dog.
Isolate dogs infected with H3N2 canine influenza for at least 21 days and dogs
infected with H3N8 CIV for at least
7 days. Practice good hygiene and
sanitation, including hand washing and thorough cleaning of shared items and
kennels, to reduce the spread of CIV. Influenza viruses do not usually survive
in the environment beyond 48 hours and are inactivated or killed by commonly
Vaccines are available for both the H3N8 and H3N2 strains of
canine influenza virus. The CIV vaccination is a "lifestyle"
vaccination, recommended for dogs at risk of exposure due to their increased
exposure to other dogs – such as boarding, attending social events with dogs
present, and visiting dog parks. Your veterinarian can provide you with
additional information about the vaccines and whether you should consider vaccinating
Frequently Asked Questions (for pet owners)
Canine Influenza reference page (for veterinarians)
Canine Influenza (Center
for Food Security and Public Health, Iowa State University)
H3N2 Frequently Asked Questions (Cornell University College of Veterinary Medicine)
Doginfluenza.com (Merck Animal Health)