The village of Bouolazou, nestled away in the sprawling bush of southern Guinea, cannot be reached by car. Only motorbikes with deep-grooved tyres can make the journey, navigating an estuary of narrow tracks that wind over rocky hills and under vast green canopies.
Those living here lead a basic life. The buildings stand squat, made of mud and brick and capped with tin roofs. There is no electricity or sanitation, while a single pump serves as the main source of water. Food can be scarce, scavenged daily from the surrounding forest.
It seems to be a largely unremarkable place – yet the blood of the village’s huntsmen and traders hold a trove of scientific secrets.
Many of these men and women, along with other villagers in the region, have been exposed to – and survived – the deadliest diseases on the planet, including Ebola, Marburg virus and Lassa Fever. There are immunological signs, too, of past Sars and Mers-like infections in the community, the likes of which have never been identified in humans before.
Dr Joseph Akoi Boré, from the nearby town of Gueckedou, made the discovery, along with academic colleagues from the universities of Oxford and Kent.
In 2017, one year after the end of the West Africa Ebola epidemic, he tested the blood of 517 bushmeat hunters and traders from dozens of villages in the forests of southern Guinea – ‘ground-zero’ of the outbreak.
The purpose of the study was to analyse the samples for Ebola antibodies and determine whether the virus had been circulating regionally before the 2013-2016 epidemic.
The results that came back surprised everyone involved.
“It was a moment I won’t forget,” says Dr Boré, a microbiologist and head of an infectious disease research centre, known as CRAM, located in Macenta.
Antibodies were found in 67 of the villagers; crucially, long-lasting antibodies that only appear five years after an Ebola infection were identified in six of the study’s participants.
“These data suggest that EBOV [the Ebola virus] has been circulating in the forested region of Guinea with mild or no reported cases prior to the 2013-16 outbreak,” the study concluded.
More than this, nearly 20 of the bushmeat hunters and traders had antibodies for Marburg virus, which can kill up to 90 per cent of people it infects, and a staggering 302 presented signs of a past infection with Lassa Fever, another viral hemorrhagic illness. One man even appeared to have been exposed to both Marburg and Ebola.
The viruses that prompted the creation of these antibodies are thought to have ‘spilled over’ from the wild animals which are regularly caught, killed and eaten by the hunters and their families.
All it takes is one unlucky exposure – a breath, a droplet, a cut or graze – for a pathogen to jump the species barrier, depending on its mode of transmission.
Bushmeat hunters run obvious risks, always probing, as they must, deeper and deeper into the forest for new sources of food.
Yet exposure to a virus doesn’t always lead to infection, thanks to the body’s immunological response. And even if it does, there’s no guarantee that a wider outbreak will follow.
Indeed, Dr Boré’s study indicates that the vast majority of pathogens spilling over into the people of Bouolazou and surrounding villages go nowhere. Unable to adapt to their new host and spread from person to person, they fizzle out and die.
But the more often the dice is rolled, the more likely it is that one of these pathogens will adapt and start to successfully spread between people. In a worst-case scenario, this transmission could spiral out of control, turning into a major epidemic, or even a pandemic.
Guinea has seen it before. The 2013-16 Ebola epidemic originated in a village close to Bouolazou after spilling over to humans from bats. The consequences were horrific: 11,000 deaths, almost 30,000 infections, and widespread economic devastation.
That so many pathogens – both known and unknown – are continuing to silently circulate in the country’s southern forests indicates that the threat of biological catastrophe has not gone away.
Analysis of the hunters’ blood shows that this risk persists in many forms – from Ebola and Marbug to mysterious coronaviruses more commonly associated with Asia. It’s also a risk present across most of the biodiverse and poorly-resourced nations of Africa, not just Guinea.
Through the ongoing work of Dr Boré and others, our knowledge of nature’s pathogenic portfolio is growing. We are identifying more and more high-risk hotspots, and better understanding how different pathogens exist and evolve in the wild.
But there is still much to learn.
Just how many outbreaks have been missed in southern Guinea? What other pathogens are lurking out in the bush? And what can be done to prevent future spillover events from occurring?
These are the questions that Dr Boré and his team are now racing to answer – before disaster strikes again.
The hunt is on. Armed with machetes and guns, and guided by the sniffing dogs at their feet, the men split up and disappear into the dense undergrowth of the bush. The light here is faint, blocked by the knotted vines and green-blooded foliage above. The air is damp and heavy.
To the uninitiated, it is an endless, maddening maze of tunnels carved into the thicket. Yet the lay of the land is instinctive to the hunters; every tree, branch and patch of soil is well known. Anything unfamiliar – a footprint in the mud, a tuft of fur – is quickly spotted.
The scent of a small antelope is soon picked up by the dogs as the group, communicating by short, sharp calls, starts to encircle its prey. The hunt quickens, only to lapse into sudden silences as the men strain to listen to the animal’s movements.
On this occasion, there’s no kill – the antelope breaks the hunting circle and is spotted darting off into the unknown. “Next time we’ll get it,” says one of the huntsmen.
But not all outings end like this. There is often success, with many different creatures of the forest brought back to Bouolazou: deers, birds, antelopes, snakes, even monkeys from time to time. Other local communities are known to regularly hunt bats and pangolins.
It is these same animals which harbour an array of “exotic and highly pathogenic viruses” capable of sickening and killing any person, says Professor Miles Carroll, an infectious disease expert at Oxford University’s Pandemic Sciences Institute and co-author of the bushmeat hunters study.
Some 1.6 million unknown viruses are estimated to lurk in the world’s mammalian and avian wildlife, up to half of which could spill into humans, while a typical rainforest – like the one in south Guinea – contains an unfathomable amount of pathogens.
“The further you push into a virgin forest, the more diseases you’re likely to uncover. It’s a numbers game,” adds Prof Carroll, a former head of research at Porton Down, the UK’s top-secret science and defence laboratory.
It’s a scary prospect, made more frightening by the fact that “there are new viruses being created all the time by Mother Nature”.
The experience of the bushmeat hunters in Bouolazou and neighbouring villages suggests that these pathogens are already coming into contact with humans.
As well as Ebola, Marburg and Lassa Fever, “we also saw a profile in their blood that showed something that’s been infecting them that has similarity with Mers virus,” says Prof Carroll.
First reported in Saudi Arabia in 2012, Mers causes a respiratory illness which has a 35 per cent case-fatality rate and is commonly spread by camels. Diseases like this aren’t usually found in Africa.
Then there’s the mysterious Covid-like antibodies which were discovered in the hunters. These were “clearly recognised” by Sars-CoV-2 in lab experiments, suggesting the pathogen responsible for their formation shares similar properties with the Covid-19 virus.
“Whatever was circulating in the hunters, it wasn’t Sars-Cov-2,” says Prof Carroll. “But it was certainly another virus we don’t know about yet.”
Whether in southern Guinea or another remote corner of Africa, the transmission of these pathogens from animal to man – and the subsequent fallout – often flies under the radar.
How a “virgin” virus mutates after spilling over into humans is crucial in explaining why. “Only if these mutations have a positive impact on the fitness of the virus in the new host is it likely to spread person to person,” and therefore spark a wider outbreak of concern, says Prof Carroll.
Yet it’s a delicate dance, especially for those living in such close proximity with nature. The smallest misstep could lead to the disturbance and emergence of a completely new disease that possesses all the characteristics needed to wreak havoc.
“We don’t know when or what will be next, or how deadly it’ll be – maybe Ebola again, Marburg, or a new disease entirely,” says Dr Boré. “We don’t know where it’ll come from – Guinea, Sierra Leone, or elsewhere. But it’s only a matter of time.”
It’s the smell that hits first – pungent, wet and acidic.
The source of the stench is the bat faeces and urine lining every surface of the darkness within. There is no escaping it, as one by one we twist our bodies to slide through the cave’s letterbox entrance, located in the heart of the jungle.
Inside, a patrol of hornet-like insects hums into life, their sharp stylets still visible in the faded light. There are signs, too, of a python lurking somewhere in the deep, we’re told. And above, hanging from the stone roof, a vast colony of bats.
It’s a subterranean world where humans don’t belong. Yet it’s into environments like these that many local hunters regularly venture, risking their health and lives with each excursion.
The bats that they catch and kill are known to carry a vast collection of viruses dangerous to humans, including Ebola and Marburg. But they’re also food.
“If we catch one, we put it into stew with rice. It is not often, but maybe once a week or once a month,” says Mamadi Ceonde, a 33-year-old hunter from the nearby village of Kilima.
“It is the same story everywhere. Our parents ate bats without problems, so we do the same. We are aware of the risk but continue to eat.”
Bats aren’t the only threat. The widespread practice of hunting for rodents is similarly fuelling the spread of diseases – in this case, Lassa Fever, a haemorrhagic illness that is endemic to southern Guinea.
The illness is carried by the multimammate mouse, which is commonly caught and eaten by child hunters, who target small rodents and birds in the forest rather than larger, harder-to-kill animals like antelopes and monkeys.
As a result, the prevalence of Lassa Fever is staggeringly high among young children, says Dr Boré, who grew up in the region.
“One of the signs is nose bleeding; in this area, you’ll see many children having a nosebleed,” he says. “I even had it when I was younger, when I was seven or eight years old. Many of my colleagues had it too.”
Why the disease doesn’t cause more harm in the region is a mystery, Dr Boré adds. While “a lot of people usually die” in the outbreaks reported elsewhere in West Africa, the communities of southern Guinea don’t report the same level of fatalities.
“Is the strain of Lassa Fever moving around these parts not as pathogenic compared to what we see in Nigeria or Sierra Leone? Or has the local population in these communities in Guinea developed higher levels of immunity? If so, how? It could be a combination of both.”
He hopes to answer these questions at a lab he is currently constructing with CRAM, and conduct further research into the spread of pathogens in the region.
The facility will also be dedicated to testing samples taken from local sick villagers in a bid to identify the cause of their illness. However, says Dr Boré, more funding is needed so they can afford equipment and a large enough generator capable of powering the whole lab.
“With what we’ve currently got, we’ll only have enough electricity to power one room at a time,” he explains. “We won’t be able to keep many of our machines running, and this will slow down our work.”
Infrastructure like this fits into wider attempts to improve the public health preparedness of the region and its ability to respond to future outbreaks.
The threat posed by Lassa Fever is certainly being taken seriously in Guinea, so much so that government health officials and experts met in September to devise a national strategy for dealing with the infection.
This plan aims to “improve the diagnosis of the disease as quickly as possible,” says Dr Pierre Tamba Kadouno, head of infections at the health department of Gueckedou prefecture.
Health officials from across Guinea are being sent to visit hospitals in Conakry, the capital, to get trained up on rapid diagnostics tests for Lassa Fever. “We are also improving our test and trace response,” says Dr Kadouno.
The government is meanwhile planning to create strategies for outbreaks of other diseases, such as Marburg virus, while each of Guinea’s 33 prefectures are in the process of training and hiring dedicated epidemiologists.
A major challenge facing these experts is how to navigate the cultural sensitivities surrounding the nation’s bush-hunting communities.
“To hunt is a way of life for these people,” says Dr Boré, adding there are roughly 3,000 huntsmen in the Macenta prefecture to which Bouolazou village belongs, and thousands more across southern Guinea.
Given the poverty of the region, and the absence of sustainable farming in the forests, there is also a clear need to venture into the bush. It’s more than just a “way of life” – it’s a means of survival.
Education is key. In the Gueckedou and Macenta prefectures, each village has its own healthcare agent, who is trained to advise residents about what infections are on the rise and how to limit their spread. These agents also regularly issue reminders on what type of animals not to eat.
“But more education is needed,” Dr Kadouno says. “Diseases have signs, which have been taught to hunter communities, so if they spot them, they know to go to the hospital. But we need to get these messages to more villages.”
Improving farming outputs, and therefore “reducing the need to go and take bushmeat,” would also help, says Prof Carroll.
“The villages don’t have great farming practices and instead keep clearing land on a regular basis when they exhaust one area. This means more encroachment and more chances of animal interaction.”
Investing in the way these communities treat and farm the soil could possibly improve the farming yield, Prof Carroll adds.
He argues that while “we can’t necessarily stop spillovers from happening, we can try to reduce the risks these people face and respond more rapidly when they happen”.
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Sarah Carter is a health and wellness expert residing in the UK. With a background in healthcare, she offers evidence-based advice on fitness, nutrition, and mental well-being, promoting healthier living for readers.