From Wikipedia, the free encyclopedia
The disease has a nearly 100% infection rate in an unvaccinated horse population that has not been previously exposed to the virus. The incubation time is one to five days.
Horses with horse flu can run a fever, have a dry hacking cough, have a runny nose, and become depressed and reluctant to eat or drink for several days but usually recover in 2 to 3 weeks.
"Vaccination schedules generally require a primary course of 2 doses, 3-6 weeks apart, followed by boosters at 6-12 month intervals. It is generally recognised that in many cases such schedules may not maintain protective levels of antibody and more frequent administration is advised in high-risk situations." 
It is a common requirement at shows in Britain that horses are vaccinated against Equine flu and a vaccination card must be produced; the FEI requires vaccination every 6 months. 
Source - http://en.wikipedia.org/wiki/Horse_flu
Equine Flu Outbreak Map - confirmed/suspect cases in Australia - last updated 12/10/2007
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Equine flu in NSW
Equine flu in QLD
Equine Influenza Australia
University Of Sydney - (Australia)
CSIRO - (Australia)
Animal Health Australia - (Australia)
Vaccination from National Office Of Animal Health - (United Kingdom)