For those non-Australian members who don't know much about the issue, Hendra Virus is basically a potentially lethal virus where the natural host is three out of four species of flying foxes. It can be transferred from horse to human, although as yet there is no evidence that it can be transferred from bat to humans.
I also know that there was a single case of a dog (maybe more?), if a horse does show positive results to Hendra Virus when they are tested - they are euthanized.
There is a 50% survival rate in humans & 70% survival rate in horses. I also know they are currently working on a vaccine and intend to have it released by 2013.