As the world wrestles with trying to end the Covid-19 pandemic, professor David Hayman is on the hunt for our next pandemic foe.
An infectious disease ecologist at Massey University, Hayman has travelled the globe looking at the spread of pathogens between wildlife and humans.
He says Covid-19 has highlighted just how connected the world really is, and points out that modern lifestyles, which are dependent on bulk resource extraction, deforestation and mono-cultural farming, have created prime conditions for a new threat to emerge.
Professor Hayman holds numerous international roles including being a member of the newly-established One Health High-Level Expert Panel. He was recently appointed the inaugural Percival Carmine chair in Epidemiology and Public Health at Massey University.
Photo: Brad Boniface Photography
Hayman tells Kim Hill the term 'One Health' describes the interconnectedness of the health of humanity and the planet - something that we must recognise if we are to reduce the numbers of novel viruses emerging in future.
“When we’re talking about One Health we’re talking about human health and animal health – and that’s both domestic animal and wildlife health and the environment’s health – are all intimately interlinked," he says.
"We can’t look at one without looking at the other."
For Hayman the scientific evidence currently points to the origins of Covid-19 being in nature and not in a lab, but nothing is certain. He says two bat virus have been discovered in China and Laos, one with a 96.8 percent genetic closeness to SARS-2. One of these viruses can directly infect human cells.
He was part of the WHO group who went to China and worked with the authorities there on the origins report.
“Most of us who work in the field assume that it’s a natural origin," he says.
"I know there’s a lot of debate as to whether it came from a lab. The current evidence since we wrote that report is that there’s been increasing evidence to support that the virus emerged around the market at Wuhan, but we really don’t know. We don’t have the first cases.
“What we’ve had since those first reports is viruses had been discovered in bats, so there were some bats in Laos that people have tested and they’ve found that are actually even closer to the previously closest known viruses, RETG 13 that was isolated in China when first reported.”
He says, although he’s making assumptions about the origin of the virus like everyone else, the early distribution of the virus case transmissions centred around the markets and not the Wuhan Institution, although we don’t know this was the source.
There were no live animals traded there and there were no pangolins for sale – the species believed to have possibly spread the virus to humans. The species has a lot of coronaviruses similar to SARS-2 but the prime suspect in the transmission of SARS-2 remains a bat.
Interestingly, he says there was already genetic diversity evident in the early cases around Wuhan market, which suggests these were either not the earliest cases of the disease and the virus had mutated, or there was more than one transmission from animals to humans.
We can expect more novel diseases like Covid-19, he says.
Incursions into the wild by deforestation or eating wild bush means we come into contact with animals who can convey viruses to humans, he says.
Scientists are discovering up to half a dozen new novel infections in humans each year and these are prevalent in certain areas of the world, he says.
“There are areas that seem to be disproportionally associated with emergence events and some of those are in, for example, tropical areas where there’s potential land use change and lots of people.
“And then when you go down to the more granular level and do the investigations you find, whether it’s Ebola outbreaks because people have picked up dead carcasses or wildlife trade, or whatever, you find those wildlife contacts that are happening.”
Hayman describes increasing human-to-wildlife interactions as low-probability high consequence events.
It's not just in Africa and far-away tropical regions this has taken place and it has been happening for a long time. Measles came from domestication of cattle thousands of years ago, he says.
“We’ve probably got all the cow infections we’re ever going to get … but what we think is happening in the tropics, whether through mining, logging or agriculture change – those changes are putting more people in contact with more different animals and more viruses and that’s like a game of Russian roulette.”
Hayman and his colleagues have been studying geographical and environmental interfaces between humans and nature, highlighting where high-risk areas are located.
He was involved in a study looking at the fragmentation of all the Ebola outbreaks in Africa and found the risk was higher not in areas where there was completely forest and not in areas where there was none, but in the intermediate ‘patchy’ forest.
He was also involved in a study in Ghana for many years, looking at bats in and around Accra.
He tested a species of bat that roosts in the city and that people eat.
"We estimate that the amount of bats that people eat in southern Ghana was about 100,000 and found the risk of contracting viruses was low."
He is currently involved in a study in Uganda, at Bwindi Impenetrable Forest, a large primeval forest located in south-western Uganda in the Kanungu District.
Public health officials discovered gorillas there got scabies from people in the community and the study looked at how human health is interacting with the gorillas' heath. The study has broadened to look at who is infecting who, with what, when and why it's happening, he says.
They are sampling what’s in the local cows, sheep, goats, gorillas and people. Locals are quizzed on their daily habits.
He says in that area bordering Congo there is a lot of connections of a lot of different species, with a lack of diagnostics and poverty, making it a higher-risk emergence interface.
“This project is really trying to understand that connectedness,” he says.
The WHO has urged countries to take precautions to avoid the spread of more novel viruses and diseases. But Hayman says our lifestyles make doing so difficult.
“There are somethings that we think you could do," he says.
"The basic things, which is improve people’s livelihoods, for example, and improve people’s access to medical diagnostics, and access to clean water.
“But there are some things like the industrial scale of moving animals around the world, the wildlife trade – not subsistence level stuff, but the industrial level stuff… Some of these things are driven by all of our lifestyles. I have an iPhone next to me that has parts which were probably mined in the Congo.
"There are a lot of things that we do that impact on things a long way away. We need to look at all those connections. Some of the farming methods are not great – expansion into tropical forests is generally bad and you still have countries that are cutting down primary forests to make space for cows and those sort of interfaces are where you’re getting the disease emergence as well.”
He says there’s a lot of focus on improving disease surveillance, which is easy. Addressing the bigger drivers will remain harder, including continued resource extraction and environmental degradation.
There is a hypothesis that when you reduce the biodiversity of the planet you include pathogens and the risk to humans. Hayman says that’s a contentious area of debate, but some reports suggest the theory can be correct.
Without balance in nature you may have species like mice proliferating and carrying illnesses like Lyme Disease around, for example.
He remains optimistic we can limit new infections, but is realistic.
“We will have more infections occur. The key thing is when you detect them and what do you stop them. That’s the sort of short-term solution. They will always happen, but we want fewer of events, and at the minute we’re seeing an increased number of events.”
