One of Australia's biggest horse racing meets, the Sydney spring carnival, was postponed indefinitely after eight of 10 horses from a Randwick stable tested positive for equine influenza.
Ian Macdonald, the primary industries minister for New South Wales state, said the quarantine would extend for 30 days from the last case of equine flu.
With that being the case it is likely racing will be shut down at Randwick for at least two months.
They were the first race horses affected by the virus.
Macdonald said there were about 700 race horses trained at the Randwick track.
Of these, the majority are expected to eventually be affected by the highly contagious illness.
"Racing and the Randwick spring carnival will come to a total halt and it has the impact of stopping racing for a considerable period of time," Macdonald said.
Several hundred recreational horses in dozens of locations throughout New South Wales and Queensland states were struck down previously by Australia's first outbreak of the flu, a respiratory disease which affects a horse for two to three weeks with a fever, hacking cough, nasal discharge and tiredness.
It is seldom fatal.
Initial estimates put losses to the country's racing industry at up to $816 million.