Canine influenza virus (CIV) causes a respiratory infection in dogs that is often referred to as “dog flu.” CIV is a relatively new virus, so almost all dogs are susceptible to infection when they are newly exposed because they have not built up natural immunity. Most dogs that develop CIV infection have a mild illness, but some dogs get very sick and require treatment in a veterinarian’s office.
Canine influenza is very contagious, meaning that it is easily spread from dogs that are currently infected to healthy dogs. CIV can pass from dog to dog through virus particles in the air (eg, through coughing or sneezing) or by coming into physical contact with other dogs (touching noses). It can also be picked up if a dog touches or plays with objects that were touched by infected dogs (for example, food bowls, toys). Humans can even transfer the virus between dogs. For example, they may spread the virus if they touch an infected dog, or even touch a toy or doorknob that the dog has contacted, and then touch another dog before washing their hands.