Outbreak of Canine Influenza Virus in the U.S.

By Dr. Megan Niederwerder

In May 2017, an outbreak of canine influenza virus (CIV) H3N2 was reported in Florida¹ and has increased concerns about this disease throughout the U.S. CIV cases associated with this outbreak have now been reported in several states, including Florida, Minnesota, Georgia, Tennessee, Texas, North Carolina, South Carolina, Kentucky, Missouri, Louisiana, and Illinois. Although CIV infection typically results in high morbidity (80% of dogs infected show clinical signs), the mortality rates are fairly low (< 10%). A recent news release from a University of Florida veterinarian reported that at least 82 dogs in Florida have been confirmed as positive for CIV since the outbreak began in May 2017 and that at least 4 of these dogs have died.²

Clinical signs
CIV primarily infects dogs, but has the potential to be transmitted to cats.³ Clinical signs are typical of respiratory infections, and include sneezing, coughing, and oculonasal discharge. Nonspecific clinical signs may include lethargy, inappetance and mild to moderate fever. Most infected dogs resolve clinical signs uneventfully and do not require veterinary intervention. In a small number of cases, pneumonia may develop, typically with a secondary bacterial infection, and clinical signs may progress to dyspnea, tachypnea, and high fever. Dogs that develop pneumonia may require hospitalization, intravenous drug therapy, supplemental oxygen and intensive supportive care.

Shedding and Vaccination
Dogs shed CIV in nasal and respiratory secretions post-infection and the virus is highly transmissible among canine populations in close contact. Although shedding is thought to be highest within the first four days post-infection, it is recommended that exposed dogs are isolated for four weeks, due to the possibility of intermittent and persistent shedding. Inactivated vaccines are available for CIV; vaccination is classified as risk-based by the American Animal Hospital Association and should be considered based on exposure risk, such as dogs who are boarded, travel, participate in dog shows, or visit dog parks frequently.

Diagnosis is typically completed through the detection of CIV nucleic acid on PCR of nasal swabs. It is ideal to collect nasal swabs at the onset of clinical signs or shortly thereafter. Lung tissue can also be tested by PCR for post-mortem diagnosis. KSVDL has an influenza PCR and also includes CIV on the Canine Respiratory Panel (together with adenovirus-2, herpesvirus-1, distemper virus, parainfluenza virus-3, respiratory coronavirus, Mycoplasma spp., and Bordetella bronchiseptica). Swabs should be submitted using 0.25 ml sterile saline, viral transport media, or the Copan-EswabTM system.

For more information on CIV, visit the AVMA website⁴ or contact KSVDL at or 866-512-5650.

¹ University of Florida. 2017. “Statement from the University of Florida College of Veterinary Medicine Regarding Canine Influenza H3N2.”

² Santich, Kate. 2017. “As dog flu outbreak widens, experts call for flu shots.”

³ University of Wisconsin-Madison. 2016. “UW Shelter Medicine, WVDL find canine influenza transmitted to cats in Midwestern shelter.”

⁴ American Veterinary Medical Association. 2017. “Canine Influenza.”

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