Gone are the days when we can say cats and dogs don't get the flu. This decade has brought surprising outbreaks in each species, making us all adjust our thoughts on infectious disease in companion animals—and the potential impact on human health. First, in February 2004, infection with the H5N1 influenza strain, or avian flu, was verified in a group of cats in one household in Thailand. In that same year, the H3N8 strain, or equine flu, was isolated in greyhounds in Florida. Since then, canine influenza has been found throughout the United States. And additional influenza A cases have been reported in both species, including H1N1 and different strains in dogs such as the virulent avian flu.
A refresher on what we now know about influenza in dogs and cats seems in order since you never know when a case might be presented to your practice or pet owners may have questions about it. Veterinary Clinics of North America: Small Animal Practice recently published a review on this topic, and a link to the full text is provided below. Here are a few of the things you'll discover.
• Which strain of flu in which species is most likely to affect your practice
• What clinical signs infected dogs and cats exhibit
• Whether the influenza strains are readily transmitted to fellow members of each species or to people
• What to tell people who fear that pets will transmit influenza to them
• Which tests will aid your diagnosis and where the tests can be performed
• What measures your clinic can take to prevent the spread of infection if a case does arise
• Why oseltamivir shouldn't be used to treat canine influenza
• What measures pet owners can take to prevent their pets from becoming infected
• How to keep abreast of current influenza research and outbreaks
• Where to learn more on how to provide basic zoonosis control and plan for handling an outbreak in your clinic
Link to full text: http://veterinarymedicine.dvm360.com/vetmed/Medicine/ArticleStandard/Article/detail/628670 
Beeler E. Influenza in dogs and cats. Vet Clin North Am Small Anim Pract 2009;39(2):251-264.