Just when we thought we had a handle on the swine flu, it turns out that another bug has been making the rounds - dog flu.  Last week the USDA announced that it had approved the first vaccine for H3N8, a flu virus that affects dogs.  So far dog flu has been found in 30 states (with Florida, New York, Philadelphia and Denver some of the hardest hit areas), although it's been occuring almost exclusively in settings where dogs are in close contact with each other, such as shelters, kennels, and doggy day care.  A vet who has been studying the H3N8 virus since 2004 found that it could be shared by dogs who just rubbed noses on the street or shared a water dish, and that humans could carry it on their clothes.

H3N8 is still not very widespread - of the 70 million dogs in the U.S., only 10,000 to 20,000 have been infected, and veterinarians are watching to see whether the dog flu mutates into something more virulent.  Right now the mortality rate among dogs that catch H3N8 is about 5 percent, and those that do die from it tend to be snub-nosed breeds such as pugs or Shi-Tzus.