Hendra virus disease in horses

The author provides an account of the discovery of a previously undescribed disease of horses and a description of the studies involved in determining the aetiology of the disease. The causative virus, now named Hendra virus (HeV), is the reference virus for a proposed new genus within the virus fam ily Paramyxoviridae. The virus is a lethal zoonotic agent able to cause nat ural disease in humans and horses and experimentally induced disease in cat s, guinea-pigs and mice. The virus also naturally infects species of the fa mily Megachiroptera, mainly subclinically, and such animals are the natural host of HeV. The virus appears to transmit readily between species of Mega chiroptera, but not readily between horses under natural and experimental c onditions, or from horses to humans. The method of transmission from bats t o horses is not known. Three incidents of HeV disease in horses have been r ecorded in Australia - two in 1994 which caused the death of two humans and fifteen horses and one in 1999 which involved the death of a single horse. Hendra virus is related to Nipah virus, the virus that caused disease and mortality in humans, pigs, dogs and cats in Malaysia during 1998 and 1999.