High Quality Content by WIKIPEDIA articles! An outbreak of equine influenza (EI) in Australia was confirmed by the New South Wales Department of Primary Industries on 24 August 2007 in Sydney. Also known as "horse flu" and "A1 influenza", the rapid outbreak was of the Influenza A virus strain of subtype H3N8. While the virus is highly contagious, it rarely kills adult horses but the performance of thoroughbred racing horses can be affected for several weeks. It can be fatal to young foals and debilitated horses.