SCIENTISTS have made a breakthrough in the fight against the deadly Hendra virus, which has killed two veterinarians in little more than a year.

Researchers from Australia and the US have shown that giving human monoclonal antibodies after exposure to Nipah virus, which is closely related to Hendra, protected animals from challenge in a disease model.

CSIRO researchers carried out the experiments at the Animal Health Laboratory in Geelong.

Hendra is a deadly virus carried by native fruit bats which can be transmitted to horses. It can then be passed on to humans.

Cases so far have been confined to Queensland.

Dr Deborah Middleton, who led the experiments, said the findings were encouraging.

"Our research clearly suggests that an effective treatment for Hendra virus infections in humans should be possible, given the very strong cross-reactive activity this antibody has against Hendra virus," she said.

First identified in Brisbane in 1994, Hendra virus has regularly infected horses in Australia. Of the 12 equine outbreaks, four have led to human infection, with four of the seven known human cases being fatal, the most recent in September.

Dr Middleton said the success of the antibody would likely depend on dose and time of administration.

"A successful application of this antibody as a post-exposure therapy will likely require early intervention," she said.

"To make clinical use of it against these viruses, it will need to be prepared under proper manufacturing guidelines, carefully evaluated again in animal models and safety tested for human use."