In September 1994, a mystery condition began affecting thoroughbred horses in Hendra, a suburb of Brisbane, Australia. A pregnant mare, Drama Series, died, followed by seven more horses in the same stable within 12 hours. The animals displayed symptoms including fever, facial swelling, respiratory distress, and spasms.
The stable owner and horse trainer, Vic Rail, became ill after treating Drama Series and died a week later. A later examination confirmed he had been infected with the same, previously unknown virus as the horses, which was named Hendra virus. Epidemiologists suspected a zoonotic disease had transferred from horses to humans.
In October 1995, a horse owner in Mackay, North Queensland, Mark Preston, also died from an illness matching symptoms seen in Rail. Retesting of blood samples from Preston and his horses, which had died in August 1994, confirmed the presence of Hendra virus antibodies. The significant distance between Hendra and Mackay, approximately 1,000 kilometres, suggested the virus was carried by a species capable of vast travel.
The search for the virus's natural host led researchers to bats. In April 1996, the first Hendra antibodies were found in black flying foxes, and subsequently in three other native Australian flying fox species. Archival blood samples from flying foxes also showed markers for Hendra from up to a dozen years prior, indicating the virus had been circulating in the wild for at least a decade before human spillover.