VALLEY STREAM - As flu season begins, many Long Islanders are preparing by getting flu shots - not only for themselves, but for their dogs, too. There's already been one confirmed case of canine flu on Long Island this season. Veterinarians say dogs that have frequent contact with other dogs, such as at a groomer's or a dog park, have a heightened risk of contracting the virus. Experts say 100 percent of dogs that are exposed to the virus will be affected by it. About 20 percent of dogs may be severely affected and require hospitalization. They say it could take a dog 4-8 weeks to recover. Veterinarians say doting pet parents can take preventative action by getting their furry friends vaccinated. Some boarding facilities already require dogs to get vaccinated before accepting them. North Shore Animal League officials say they recommend a dog flu shot before all adoptions. Symptoms of dog flu include runny nose, cough, fever and loss of appetite. Most vets on Long Island offer the shot for around $30.