The signs of canine influenza virus (CIV) infection are mild in most dogs and are similar to those of canine cough.

Pet care professionals must have a high index of suspicion to ensure appropriate identification, management, and prevention of disease transmission.

Red Flags for CIV Infection

CIV cannot be distinguished from other causes of acute respiratory disease based on clinical signs alone. A definitive diagnosis can be made using laboratory testing, but results with some methods are not immediate, and other tests may cause false-negative results due to the critical timing of sample collection based on the time of exposure and peak virus shedding. To learn more about how to accurately diagnose canine influenza, click here.

Veterinarians, and others who provide care for dogs that are in close contact, should have a high index of suspicion for CIV. If it is recognized early, spread to other dogs can be minimized. Red flags that may indicate CIV infection include:^2,8

• High-risk dogs (eg, a dog transferred from a CIV-endemic area; a recent intake of a dog from a shelter or racing track) that have recently been introduced into the population.
• Sudden increase in the prevalence of acute respiratory disease in a population of dogs. When CIV is introduced into a group of dogs that have not been previously exposed, CIV usually leads to an explosive onset and spread of "canine cough" that affects most dogs, often in less than 2 weeks. However, once canine influenza is established in a population, this pattern is no longer apparent.
• More severe course of illness than typically occurs with canine cough.
• Dogs that are already vaccinated for other canine respiratory diseases.
• Prolonged or complete lack of response to antibiotic therapy targeted at Bordetella bronchiseptica.

It is important to note that dogs of all ages are susceptible to infection with CIV. In addition, prior vaccination against canine distemper virus, adenovirus type 2, parainfluenza virus, and B. bronchiseptica does not prevent the introduction and spread of CIV.²