A horse veterinarian died from the Hendra virus earlier this month and five horses were destroyed after an outbreak at the Redlands Veterinary Clinic in south-east Queensland.
Researchers are looking into a rising number of flying fox-related viral outbreaks in other parts of the world, including the deadly ebola virus in Africa and the 2003 SARS epidemic in southern China.
CSIRO virologist Dr Linfa Wang has told the ABC's Background Briefing there is an emerging theory that the animals' immune systems are reacting to human interference.
"Some people even propose that the virus [is] good for bats," he said.
"It's like a biological weapon protect their ecological niche. Only when humans try to destroy that balance that the virus jumps out."