The first reported case in NSW of Australian bat lyssavirus – a rare disease closely related to the notorious rabies – resulted in the death of a man in his 50s this week, several months after his exposure to the infection.

It’s the fourth confirmed case in Australia since 1996, and all have been fatal. But what is Australian bat lyssavirus, and should Australians be worried? Here’s what to know.

Lyssaviruses are a group of RNA viruses that are transmitted to humans with a bite or a scratch from an infected animal. Australian bat lyssavirus falls under this umbrella, as does the deadly virus rabies, which is not identical to Australian bat lyssavirus though they are closely related.

Currently, rabies does not occur in land-living animals in Australia. Australian bat lyssavirus, however, does occur in Australia and is transmitted to humans from bats. Like rabies, which is one of the most notorious and hard-to-treat diseases humans can catch from animals, once symptoms develop, Australian bat lyssavirus is fatal.

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Four cases of Australian bat lyssavirus infections in humans have been recorded since the virus was identified in 1996. Three of those cases were in Queensland, the most recent being in 2013 when an eight-year-old boy died after being bitten by an infected bat while holidaying in the Whitsundays. The first confirmed case in NSW resulted in the death of a man in his 50s this week.

According to a 2018 article from the Australian Journal of General Practice, it’s estimated that Australian bat lyssavirus is prevalent in less than 1 per cent of healthy bats. In sick, injured or orphaned bats, that prevalence rate is estimated to be between 5 and 10 per cent. Overall, there’s a total population prevalence estimate of less than 0.5 per cent, per another 2018 study.

Between January and June 2021, Wildlife Health Australia reported 27 cases of Australian bat lyssavirus in bats across Australia, with 14 occurring in Queensland, nine in NSW and two each in South Australia and Victoria. At June 2023, according to Wildlife Health Australia, there were 407 reported cases of Australian bat lyssavirus in bats across Australia over 28 years, since 1995.

Keira Glasgow, a director in health protection at NSW Health, said on Wednesday that people should assume any bat in Australia could be carrying Australian bat lyssavirus. That includes flying foxes, other fruit bats and insect-eating microbats.

Like rabies, a bite or a scratch from an infected bat is how Australian bat lyssavirus is transmitted to humans. It can also be transmitted by other exposure through the eyes, nose or mouth to an infected animal’s saliva. It’s for this reason, Glasgow said, only trained and vaccinated wildlife workers should handle bats, and NSW Health advises in general to avoid handling any land-dwelling wild or domestic mammal in countries with a rabies virus risk.

NSW Health advises anyone who sees a bat distressed, injured or trapped on the ground to not try to rescue it. Instead, people should call WIRES’ trained experts on 1300 094 737 or local wildlife groups.

Australian bat lyssavirus affects the central nervous system, with early symptoms being described as flu-like, including headaches, fever and fatigue. Eventually, the illness progresses to paralysis, with convulsions and delirium. Death usually comes within a fortnight of symptoms presenting.

According to NSW Health, the previous three human cases of Australian bat lyssavirus had wide variability when it came to their incubation periods, as some took several days and others several years for symptoms to present.

Hendra is another rare disease that’s passed from an infected horse to humans, with very few reported human cases in Australia. Since 2012, a vaccine for horses has been available.

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Hendra virus, believed to be transmitted from flying foxes to horses via contaminated bat urine, droppings or saliva, is not the same as equine flu, which is highly contagious among horses but does not infect humans.

It’s also believed that Hendra virus is not transmitted to humans directly from flying foxes, only through human contact with an infected horse’s bodily fluids. Human-to-human Hendra virus transmission has also not been reported.

One fortunate aspect of Australian bat lyssavirus being so closely related to rabies is that rabies prevention measures can effectively protect humans from Australian bat lyssavirus when symptoms are detected early.

“It is incredibly rare for the virus to transmit to humans, but once symptoms of lyssavirus start in people who are scratched or bitten by an infected bat, sadly there is no effective treatment,” Glasgow said. “If you are bitten or scratched by a bat, urgent medical assessment is crucial.”

NSW Health said that in 2024, 118 people required medical assessment after being bitten or scratched by bats. The man who died this week received treatment several months ago after being bitten by a bat. Glasgow said further investigation was under way “to understand whether other exposures or factors played a role in his illness”.

Meanwhile, Dr Alison Peel, a veterinarian and wildlife disease ecologist at the University of Sydney, told this masthead that it’s not the time to panic or “persecute bats”, as they are essential to our ecosystems.