A virus that is very similar to the deadly Nipah and Hendra viruses has been discovered in fruit bats in Australia and researchers are hoping it can help them find ways to fight those highly dangerous cousins.

The Nipah virus kills 40-75 percent of the people it infects while the Hendra virus, which normally affects horses, kills more than 50 percent of the people it infects.

But the newly discovered Cedar virus, with 90 percent of its genes identical to those of Hendra and Nipah, failed to cause any disease when researchers injected it into rats, guinea pigs and ferrets, they wrote in a paper published on Friday in the journal PLoS Pathogens (Public Library of Science).

They are now comparing the DNA of all three viruses to tease out genes that are responsible for the deadliness of the Nipah and Hendra, said lead author Gary Crameri, at the Commonwealth Scientific and Industrial Research Organisation's Australian Animal Health Laboratory.

"We have already done genetic analyses and identified those things that are different between Hendra/Nipah and the Cedar," Crameri said in a telephone interview.

"Our plan now is to genetically engineer these viruses so we can take some parts of the Hendra genome that don't appear in Cedar but play some role in how deadly they are, put them into Cedar and then do infection trials with the new hybrid virus and see if it is as deadly."

Researchers hope to home in on the rogue genes to find cures for Nipah and Hendra, which are also found in bats.

"There is no secret that the pathogenicity of the Hendra and Nipah lie in their genes and this will help us narrow down some of the options. From there, we can start to think about therapeutic approaches, new drugs that we can use to target these viruses so that when people get infected, we can treat them, something we don't have now," Crameri said.

Bats are a natural reservoir for many viruses, including highly pathogenic ones like rabies, Ebola, SARS, Hendra and Nipah. Although Cedar appears not to cause any disease in the few animal species that researchers tested the virus on, it is not known if it causes disease in people.

A Nipah outbreak in 1998 killed at least 105 pig farmers in Malaysia and one abattoir worker in Singapore. There have been numerous outbreaks since in Bangladesh and India.

While the cases in Malaysia and Singapore were due to contact with infected pigs, the South Asian outbreaks were mostly due to consumption of raw date palm juice that had been contaminated with urine or droppings from infected fruit bats.

The Hendra virus kills 75 percent of the horses it infects. While it rarely jumps from horse to people, four of the 7 human cases recorded since 1994 in Australia have resulted in death.