Detection of a novel Hendra virus in the urine of Australian bats and flying foxes has been reported in a new study. Hendra virus – a deadly virus transmitted by bats – has been known previously to spill over into horses and then into humans, but the new variant expands on the potential geographical risk the virus poses and suggests flying foxes may act as a reservoir. 

The results were published in the journal Emerging Infectious Diseases. 

Hendra virus is an emerging infectious disease, according to the World Health Organization, that affects horses and rarely humans, causing severe disease in both that often leads to death. It is currently geographically restricted to Australia – namely the East coast, where outbreaks have centered around Brisbane and east Queensland.

Symptoms of the virus range in severity, from classical flu-like symptoms to fatal respiratory and neurological disease. Once infected, treatment is limited to standard intensive care responses, though monoclonal antibody therapies are currently under investigation. The most effective method of combatting Hendra virus currently available is an animal vaccine to prevent the spread through horses, which is then the most common path that Hendra virus uses to jump to humans. 

The most recent investigation, performed by a collaboration of scientists from various institutions across Australia, looked into a recent spillover event of a novel Hendra virus into a single horse in New South Wales, resulting in its death. The horse tested negative for the virus – until a test that was updated for a novel variant, called HeV-g2, recorded a positive test result. When compared to urine samples taken from a grey-headed flying fox, the variant showed a 99 percent similarity, suggesting the virus likely made an interspecies jump. 

After placing a sheet underneath flying fox roosts in Queensland for a period of four years, the researchers collected urine samples and screened them for the presence of Hendra virus. The team used an updated qRT-PCR analysis method to allow for the detection of the novel HeV-g2 variant, which standard screening methods cannot. In total, over 4,500 pooled urine samples were collected and a further 1,674 samples were also gained from individual bats during catching sessions. 

They discovered the new variant was present in a total of ten samples across all seasons and in multiple species of flying fox, suggesting the HeV-g2 variant could already be prevalent across these populations and may present a distinct spillover risk. It also demonstrated the variant was now more geographically widespread than previously known, and the variant must be more closely monitored to improve animal care guidelines to prevent human cases. 

The researchers now hope a more comprehensive diagnostic system can be implemented to monitor the distribution of the Hendra virus variants, particularly due to the lethality and lack of treatment options available should it spill over to humans.