How a gruesome outbreak in a Brisbane suburb sparked a hunt that might help us uncover the origins of COVID-19.
WARNING: this story contains images and descriptions that some readers may find distressing.
It was a blustery Thursday afternoon in suburban Brisbane; the last chills of winter were disappearing and the jacaranda trees looked just about ready to blossom.
On a quiet street about 15 minutes north-east of the city, kids were out riding their bikes.
It looked like any average suburban street — except that on this particular day in September, 1994, it was anything but.
Horses were being cut up in the front yard of a local stable by vets from the Department of Primary Industries, and the street was literally running with blood.
"There were a lot of body parts and blood and tissue leaking into the ground, so much so that some of the blood was running through the driveway, into the gutter," says local vet Peter Reid, who had been treating the horses before they died.
The DPI vets were trying to get to the bottom of what had suddenly killed several horses at the suburban stable. But there was little in the way of infection control.
"Some of the owners of the horses — without any personal protection — were bagging up the heads of the horses and brains and body parts … and dumping them into the back of an open semi-trailer," Dr Reid says.
"Then there was a crane operating, which was winching the horses — which had been opened with all the tissue and blood dripping out — across the footpath and street. It was horrendous."
Loading...People from the neighbourhood soon began crowding around.
"Young kids from the area were zooming around on their bikes, splashing this stuff," says veteran racing commentator and journalist Helen Thomas.
"People were hosing out as much as they could, but all this stuff — blood and literally guts — was flying down the road."
No-one knew what had caused these horses to suddenly die, or whether humans were at risk of being exposed to whatever had killed them.
"We didn't know what we were dealing with," Ms Thomas says.
"It beggars belief now."
It started with one mare
The stable at the centre of this horror-scene belonged to renowned Queensland horse trainer, Vic Rail.
Vic had a reputation in racing circles for being a colourful character, but was considered "one of Queensland's leading trainers at the time", says Ms Thomas.
Vic and his partner Lisa were managing two dozen horses at their stables in Hendra, a suburb that had become the racing hub of south-east Queensland.
Loading...A couple of weeks prior to the gruesome public autopsy, Vic and Lisa had called Dr Reid out to take a look at a pregnant thoroughbred named Drama Series that had been brought in from the paddock looking unwell.
"She was having difficulty walking and had some swelling around her head," says Dr Reid, an equine vet surgeon who was working mostly with race horses.
"She'd lost body weight, she was running a temperature, and she was very reluctant to move."
It wasn't clear what was making Drama Series so unwell. After administering some antibiotics and anti-inflammatories, Dr Reid told Vic and Lisa to call him if things got worse.
Loading...At 4:00am, his phone rang.
"By the time I got here … she was dead. That was probably within half an hour."
The mystery illness spreads
Two weeks later, Dr Reid got another call to say the stables were now full of sick horses, many with the same symptoms.
"It was very difficult to try and treat them — a lot of them were unstable on their feet, and in some cases, dangerous to examine," he says.
With no clear diagnosis, and some of the horses in significant distress, Dr Reid had no choice but to start euthanasing them.
"One particular horse I remember had collapsed and was thrashing [on the ground]," he says.
"I went in to try and put a needle in his neck — that's how we put horses down — but he was thrashing that much that I couldn't physically do it."
The speed at which the horses were collapsing was like nothing Dr Reid had ever seen.
"In the space of 12 hours, I think there were seven horses."
He suspected a toxin or poison might be to blame, but couldn't find any evidence of either.
"There was nothing I'd ever read about in any of the literature that could have done this," he says.
Blood tests were inconclusive, but pathology reports showed the horses had suffered haemorrhages throughout their body and essentially drowned in their own fluids.
Then came another piece to the puzzle.
From horses to humans
As the mysterious outbreak unfolded, Vic himself became unwell.
"He went to the races and came home that afternoon with complaints of aching joints, sore in the groin, just generally very sick, high fever," Lisa told ABC Radio National in 1995.
Vic was taken to hospital, and alarm bells started to ring. Had Vic caught whatever the horses had?
Vic's reputation helped catapult the outbreak into national and international headlines.
"It stopped Queensland racing for about a week and there was great fear that it was something that was going to spread through the horse population in Australia," Ms Thomas says.
Vic was the first person who had been around the horses to become sick, but he wasn't the only one.
Shortly after he was hospitalised, one of Vic's stable hands, Ray Unwin, also became unwell.
With people now seemingly infected, Queensland Health was called in to investigate.
Linda Selvey, who had just joined the department as a trainee infectious disease epidemiologist, was tasked with finding out whether the mystery disease was spreading among people.
"It was quite puzzling," says Dr Selvey, an associate professor in the school of public health at the University of Queensland.
"We weren't aware of anything that was quite like this."
With limited knowledge, Dr Selvey and her colleagues cast a wide net, talking to scientists from the World Health Organization and hitting the streets in Hendra to find out more.
"I knocked on the doors of neighbours and asked them about symptoms and took blood from people who had symptoms," she says.
Just a few days into the investigation, the stakes got even higher.
'Just like the horses'
Lisa got a call from the hospital to say Vic's condition had suddenly deteriorated.
"They explained to me that they had to put him on a life support system because his lungs had all but closed up," she told filmmaker Brian Benson, who was shooting a documentary on the outbreak.
"It was just like the horses."
Not long after, Vic suffered a cardiac arrest and died.
"People were shocked because he was one of those larger-than-life characters that people really loved," says Ms Thomas.
Loading..."I think there was a sense of disbelief: how could a trainer or any relatively young man — he was only 49 — die so quickly?
"What happened? What was it? No-one really understood the sequence of events."
Never seen before
As waves of shock and fear rippled through the racing community, scientists were getting closer to cracking the mystery.
The samples from the horses cut up in Lisa and Vic's front yard had made their way to one of the most secure labs in the country: the Australian Animal Health Laboratory (AAHL) in Geelong.
"It's a box within a box within a box — three layers of containment," says Linfa Wang, who was working there as a junior molecular biologist.
At the AAHL, a small group of Australia's top scientists began working out exactly what pathogen was lurking inside the horses.
Within a week, the team had managed to isolate a virus.
What they found looked closest to a morbillivirus — a genus of viruses that usually cause respiratory and gastrointestinal problems — so they tentatively named it "equine morbillivirus".
But it would take another year to map out the virus's genome, at which point the researchers realised it was different to anything they'd seen before.
Loading..."It's a totally new virus — it does not belong to any of the existing virus classifications," says Professor Wang, now director of the Emerging Infectious Diseases Program at Duke-NUS Medical School in Singapore.
The team decided to call it "Hendra virus" after the Brisbane suburb where it was first discovered.
"At that time, we still did not know how this virus jumped out, or why we see this first in Australia," Professor Wang says.
Where had the virus come from?
In Hendra, it took authorities a few months to bring the outbreak under control: 13 horses died and 20 became sick. Fortunately, no-one else besides Ray Unwin — who eventually recovered — got sick.
Still, no-one could figure out where the virus had come from.
Queensland authorities needed to find its natural host — the species in which the virus lives, grows and multiplies — to reduce the risk of it popping up again.
So the Department of Primary Industries began looking for evidence of the virus in other animals in the area.
"There was trapping of possums and cats, and bleeding of dogs and chickens and all sorts of things," says Kim Halpin, a veterinary virologist at the CSIRO in Geelong.
"They sampled over 4,000 animals, and from that, they had absolutely no positive results."
Then, scientists got another clue.
Was Vic patient zero?
In August 1994, a month before the outbreak in Hendra, two horses had unexpectedly died in Mackay, about 1,000 kilometres north of Brisbane.
One of the horses' owners, Mark Preston, had also fallen mysteriously ill, recovered, and then died suddenly a year later.
By retesting old samples, health authorities discovered Mark Preston and his horses had also been infected with Hendra virus.
The virus had been circulating for longer and across a wider area than anyone had realised.
The discovery prompted authorities to go back to the drawing board, and Dr Halpin was brought onto the case to investigate.
"We needed an animal species that had the opportunity to come into contact with horses, a species that was present in both locations, and probably a species where you had overlapping populations, to explain the appearance of the virus in two different places at the same time," she says.
That pointed to something that could fly. But Hendra virus had been identified as a mammalian virus, so it was unlikely to have been hiding in birds.
"The species that fitted all of these points was flying foxes," Dr Halpin says.
After months of work collecting samples from bats all over Brisbane, Dr Halpin was finally able to isolate the virus from a bat found in the inner-city.
"That was an ‘aha' moment," she says.
Loading...While it's difficult to prove that a species is a true host of a virus (and not just a carrier), all the evidence pointed to bats.
"Horses are very inquisitive animals — if they're out in a paddock and maybe a flying fox is close by and it's in a tree, it might drop some chewed up fruit to the ground, horses will go over and investigate that," says Dr Halpin.
Drama Series had been eating the bark and leaves of a fruit tree not long before she was found.
A groundbreaking discovery
In 2021, bats being the source of a mysterious new virus isn't all that surprising.
After all, bats are suspected to have played a role in transferring SARS-CoV-2 — the virus that causes COVID-19 — to humans, and are well recognised as a source of emerging animal-to-human diseases. But in the mid 90s, bats weren't really on people's radar.
"Hendra really was a bit of a watershed moment when bats and viruses essentially came out of the forest and we had a spillover event in suburbia that went on to have catastrophic consequences," Dr Halpin says.
The discovery of Hendra virus has had major implications for our understanding of how diseases spread from animals to humans.
As Professor Wang explains, "Beyond any doubt our work on Hendra virus and the connection to bats lay the groundwork for many, many more major outbreak responses — Nipah, SARS, Ebola, and now COVID-19."
Bats have become central to discussions about emerging infectious diseases, and are being closely studied to help understand the source of the next pandemic.
As humans push into natural environments, and live in closer proximity to animals, there are more opportunities for viruses to spill over, Dr Halpin says.
"As flying foxes have lost their habitat, they've really had to come into suburbia to survive, and with that comes the viruses they carry."
Research shows new infectious diseases — more than 70 per cent of which come from animals — have been increasing steadily over the last three decades.
"There are many factors, but I think it's human behaviour," Professor Wang says.
"We're talking about climate change, transportation, intensive farming, and wildlife trading."
Outbreaks of emerging viruses from bats are unavoidable, he says.
"I don't think we can predict the next pandemic. But what we can do is really take the warning seriously and work together."
The lasting impacts of Hendra
Since the first documented outbreak in 1994, Hendra virus has killed four people in Australia.
Another three people — all vets or people caring for horses — have become infected and very unwell.
The virus is estimated to kill 60 per cent of people it infects. For horses, it's even more fatal: so far, more than 100 animals have died.
After multiple outbreaks across Queensland and NSW, scientists made a breakthrough with the development of a vaccine for horses in 2012. But in recent years, vaccine uptake has slowed. This hesitancy frustrates those who witnessed the horror of the virus firsthand.
Dr Reid says once you've seen a horse die from Hendra, it's hard to forget.
"I would say it's probably the worst disease a horse could get, not only for the way it ultimately kills most of them … but the virus actually attacks all the blood vessels in the body," he says.
"It's terrifying."
For Dr Reid, Hendra virus — and the early days of the outbreak at the stables in Brisbane — are never too far from his mind.
"My wife actually said to me once that although it didn't get me, she was still a Hendra widow, because of the waking hours and effort I've put into trying to prevent it ever happening again."
This story comes from Patient Zero, an eight-part series about disease outbreaks. Listen for free wherever you get your podcasts.
Credits
Additional reporting and research: Carl Smith
Editor and digital producer: Annika Blau
Executive producer: Joel Werner
Photographs supplied by John Sheridan; videos courtesy Brian Benson (State Library of QLD) and ABC archive, edited by Sophie Kesteven