'Tip of the
iceberg': is our destruction of nature responsible for Covid-19?
As habitat
and biodiversity loss increase globally, the coronavirus outbreak may be just
the beginning of mass pandemics
The age of
extinction is supported by
Band
Foundation and Wyss FoundationAbout this content
John Vidal
Wed 18 Mar
2020 06.00 GMTLast modified on Thu 19 Mar 2020 20.41 GMT
A dead
monkey sold as bushmeat hangs outside a villager’s house in north-east Gabon.
A dead monkey sold as bushmeat hangs outside a
villager’s house in north-east Gabon. Photograph: Christine Nesbitt/AP
Mayibout 2
is not a healthy place. The 150 or so people who live in the village, which
sits on the south bank of the Ivindo River, deep in the great Minkebe Forest in
northern Gabon, are used to occasional bouts of diseases such as malaria,
dengue, yellow fever and sleeping sickness. Mostly they shrug them off.
But in
January 1996, Ebola, a deadly virus then barely known to humans, unexpectedly
spilled out of the forest in a wave of small epidemics. The disease killed 21
of 37 villagers who were reported to have been infected, including a number who
had carried, skinned, chopped or eaten a chimpanzee from the nearby forest.
I travelled
to Mayibout 2 in 2004 to investigate why deadly diseases new to humans were
emerging from biodiversity “hotspots” such as tropical rainforests and bushmeat
markets in African and Asian cities.
It took a
day by canoe and then many hours along degraded forest logging roads, passing
Baka villages and a small goldmine, to reach the village. There, I found
traumatised people still fearful that the deadly virus, which kills up to 90%
of the people it infects, would return.
Villagers
told me how children had gone into the forest with dogs that had killed the
chimp. They said that everyone who cooked or ate it got a terrible fever within
a few hours. Some died immediately, while others were taken down the river to
hospital. A few, like Nesto Bematsick, recovered. “We used to love the forest,
now we fear it,” he told me. Many of Bematsick’s family members died.
Only a
decade or two ago it was widely thought that tropical forests and intact
natural environments teeming with exotic wildlife threatened humans by
harbouring the viruses and pathogens that lead to new diseases in humans such
as Ebola, HIV and dengue.
3D print of
a spike protein and a Covid-19 virus particle
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A 3D print of a spike protein and a Covid-19 virus particle. On the virus model
(behind), the virus surface (blue) is covered with spike proteins (red) that
enable the virus to enter and infect human cells. Photograph: National
Institutes of Health/AFP via Getty Images
But a
number of researchers today think that it is actually humanity’s destruction of
biodiversity that creates the conditions for new viruses and diseases such as
Covid-19, the viral disease that emerged in China in December 2019, to arise –
with profound health and economic impacts in rich and poor countries alike. In
fact, a new discipline, planetary health, is emerging that focuses on the
increasingly visible connections between the wellbeing of humans, other living
things and entire ecosystems.
Is it
possible, then, that it was human activity, such as road building, mining,
hunting and logging, that triggered the Ebola epidemics in Mayibout 2 and
elsewhere in the 1990s and that is unleashing new terrors today?
“We invade
tropical forests and other wild landscapes, which harbour so many species of
animals and plants – and within those creatures, so many unknown viruses,”
David Quammen, author of Spillover: Animal Infections and the Next Pandemic,
recently wrote in the New York Times. “We cut the trees; we kill the animals or
cage them and send them to markets. We disrupt ecosystems, and we shake viruses
loose from their natural hosts. When that happens, they need a new host. Often,
we are it.”
Increasing
threat
Research
suggests that outbreaks of animal-borne and other infectious diseases such as
Ebola, Sars, bird flu and now Covid-19, caused by a novel coronavirus, are on
the rise. Pathogens are crossing from animals to humans, and many are able to
spread quickly to new places. The US Centers for Disease Control and Prevention
(CDC) estimates that three-quarters of new or emerging diseases that infect
humans originate in animals.
Bats are
trapped in nets
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Bats are trapped in nets to be examined for possible viral load at the
Franceville International Centre of Medical Research in Gabon. Photograph:
Steeve Jordan/AFP via Getty Images
Some, like
rabies and plague, crossed from animals centuries ago. Others, such as Marburg,
which is thought to be transmitted by bats, are still rare. A few, like
Covid-19, which emerged last year in Wuhan, China, and Mers, which is linked to
camels in the Middle East, are new to humans and spreading globally.
Other
diseases that have crossed into humans include Lassa fever, which was first
identified in 1969 in Nigeria; Nipah from Malaysia; and Sars from China, which
killed more than 700 people and travelled to 30 countries in 2002–03. Some,
like Zika and West Nile virus, which emerged in Africa, have mutated and become
established on other continents.
Kate Jones,
chair of ecology and biodiversity at UCL, calls emerging animal-borne
infectious diseases an “increasing and very significant threat to global
health, security and economies”.
Amplification
effect
In 2008,
Jones and a team of researchers identified 335 diseases that emerged between
1960 and 2004, at least 60% of which came from animals.
Increasingly,
says Jones, these zoonotic diseases are linked to environmental change and
human behaviour. The disruption of pristine forests driven by logging, mining,
road building through remote places, rapid urbanisation and population growth
is bringing people into closer contact with animal species they may never have
been near before, she says.
The
resulting transmission of disease from wildlife to humans, she says, is now “a
hidden cost of human economic development. There are just so many more of us,
in every environment. We are going into largely undisturbed places and being
exposed more and more. We are creating habitats where viruses are transmitted
more easily, and then we are surprised that we have new ones.”
Kate Jones
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Kate Jones warns of ‘a very significant threat to global health, security and
economies’. Photograph: Courtesy of Kate Jones
Jones
studies how changes in land use contribute to the risk. “We are researching how
species in degraded habitats are likely to carry more viruses which can infect
humans,” she says. “Simpler systems get an amplification effect. Destroy
landscapes, and the species you are left with are the ones humans get the
diseases from.”
“There are
countless pathogens out there continuing to evolve which at some point could
pose a threat to humans,” says Eric Fevre, chair of veterinary infectious
diseases at the University of Liverpool’s Institute of Infection and Global
Health. “The risk [of pathogens jumping from animals to humans] has always been
there.”
The
difference between now and a few decades ago, Fevre says, is that diseases are
likely to spring up in both urban and natural environments. “We have created
densely packed populations where alongside us are bats and rodents and birds,
pets and other living things. That creates intense interaction and
opportunities for things to move from species to species,” he says.
Tip of the
iceberg
“Pathogens
do not respect species boundaries,” says disease ecologist Thomas Gillespie, an
associate professor in Emory University’s department of environmental sciences,
who studies how shrinking natural habitats and changing behaviour add to the
risk of diseases spilling over from animals to humans.
Thomas
Gillespie with primatologist Jane Goodall
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Disease ecologist Thomas Gillespie with primatologist Jane Goodall. Photograph:
Courtesy of Thomas Gillespie
“I am not
at all surprised about the coronavirus outbreak,” he says. “The majority of
pathogens are still to be discovered. We are at the very tip of the iceberg.”
Humans,
says Gillespie, are creating the conditions for the spread of diseases by
reducing the natural barriers between host animals – in which the virus is
naturally circulating – and themselves. “We fully expect the arrival of
pandemic influenza; we can expect large-scale human mortalities; we can expect
other pathogens with other impacts. A disease like Ebola is not easily spread.
But something with a mortality rate of Ebola spread by something like measles
would be catastrophic,” Gillespie says.
Wildlife
everywhere is being put under more stress, he says. “Major landscape changes
are causing animals to lose habitats, which means species become crowded
together and also come into greater contact with humans. Species that survive
change are now moving and mixing with different animals and with humans.”
Gillespie
sees this in the US, where suburbs fragment forests and raise the risk of
humans contracting Lyme disease. “Altering the ecosystem affects the complex
cycle of the Lyme pathogen. People living close by are more likely to get
bitten by a tick carrying Lyme bacteria,” he says.
Logging
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The disruption of pristine forests driven by
logging, mining, road building, rapid urbanisation and population growth is
bringing people into closer contact with wildlife, increasing the risk of
disease. Photograph: Samir Tounsi/AFP/Getty Images
Yet human
health research seldom considers the surrounding natural ecosystems, says
Richard Ostfeld, distinguished senior scientist at the Cary Institute of
Ecosystem Studies in Millbrook, New York. He and others are developing the
emerging discipline of planetary health, which looks at the links between human
and ecosystem health.
“There’s
misapprehension among scientists and the public that natural ecosystems are the
source of threats to ourselves. It’s a mistake. Nature poses threats, it is
true, but it’s human activities that do the real damage. The health risks in a
natural environment can be made much worse when we interfere with it,” he says.
Ostfeld
points to rats and bats, which are strongly linked with the direct and indirect
spread of zoonotic diseases. “Rodents and some bats thrive when we disrupt
natural habitats. They are the most likely to promote transmissions [of
pathogens]. The more we disturb the forests and habitats the more danger we are
in,” he says.
Felicia
Keesing, professor of biology at Bard College, New York, studies how
environmental changes influence the probability that humans will be exposed to
infectious diseases. “When we erode biodiversity, we see a proliferation of the
species most likely to transmit new diseases to us, but there’s also good
evidence that those same species are the best hosts for existing diseases,” she
wrote in an email to Ensia, the nonprofit media outlet that reports on our
changing planet.
The market
connection
Disease
ecologists argue that viruses and other pathogens are also likely to move from
animals to humans in the many informal markets that have sprung up to provide
fresh meat to fast-growing urban populations around the world. Here, animals
are slaughtered, cut up and sold on the spot.
The “wet
market” (one that sells fresh produce and meat) in Wuhan, thought by the
Chinese government to be the starting point of the current Covid-19 pandemic,
was known to sell numerous wild animals, including live wolf pups, salamanders,
crocodiles, scorpions, rats, squirrels, foxes, civets and turtles.
Dead
pangolins seized in North Sumatra
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Dead pangolins seized by authorities in North Sumatra. Disease ecologists argue
that viruses and other pathogens are likely to move from animals to humans in
wildlife markets. Photograph: Gatha Ginting/AFP via Getty Images
Equally,
urban markets in west and central Africa sell monkeys, bats, rats, and dozens
of species of bird, mammal, insect and rodent slaughtered and sold close to
open refuse dumps and with no drainage.
“Wet
markets make a perfect storm for cross-species transmission of pathogens,” says
Gillespie. “Whenever you have novel interactions with a range of species in one
place, whether that is in a natural environment like a forest or a wet market,
you can have a spillover event.”
The Wuhan
market, along with others that sell live animals, has been shut by the Chinese
authorities, and last month Beijing outlawed the trading and eating of wild
animals except for fish and seafood. But bans on live animals being sold in
urban areas or informal markets are not the answer, say some scientists.
“The wet
market in Lagos is notorious. It’s like a nuclear bomb waiting to happen. But it’s
not fair to demonise places which do not have fridges. These traditional
markets provide much of the food for Africa and Asia,” says Jones.
“These
markets are essential sources of food for hundreds of millions of poor people,
and getting rid of them is impossible,” says Delia Grace, a senior
epidemiologist and veterinarian with the International Livestock Research
Institute, which is based in Nairobi, Kenya. She argues that bans force traders
underground, where they may pay less attention to hygiene.
A bushmeat
stall in Equatorial Guinea
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A bushmeat stall with pangolins, bush rats and
tiger cats for sale on the roadside outside Bata in Equatorial Guinea.
Photograph: Carl de Souza/AFP/Getty Images
Fevre and
colleague Cecilia Tacoli, principal researcher in the human settlements
research group at the International Institute of Environment and Development
(IIED), argue in a blog post that rather than pointing the finger at wet
markets, we should look at the burgeoning trade in wild animals.
“It is wild
animals rather than farmed animals that are the natural hosts of many viruses,”
they write. “Wet markets are considered part of the informal food trade that is
often blamed for contributing to spreading disease. But … evidence shows the
link between informal markets and disease is not always so clear cut.”
Changing
behaviour
So what, if
anything, can we do about all of this?
Jones says
that change must come from both rich and poor societies. Demand for wood,
minerals and resources from the global north leads to the degraded landscapes
and ecological disruption that drives disease, she says. “We must think about
global biosecurity, find the weak points and bolster the provision of health
care in developing countries. Otherwise we can expect more of the same,” she
adds.
“The risks
are greater now. They were always present and have been there for generations.
It is our interactions with that risk which must be changed,” says Brian Bird,
a research virologist at the University of California, Davis School of
Veterinary Medicine One Health Institute, where he leads Ebola-related
surveillance activities in Sierra Leone and elsewhere.
“We are in
an era now of chronic emergency,” Bird says. “Diseases are more likely to
travel further and faster than before, which means we must be faster in our
responses. It needs investments, change in human behaviour, and it means we must
listen to people at community levels.”
A poster in
Beijing promoting wildlife as friends instead of food
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A poster in Beijing promoting wildlife as friends instead of food, after a
crackdown on wild animal markets following the coronavirus outbreak.
Photograph: Andy Wong/AP
Getting the
message about pathogens and disease to hunters, loggers, market traders and
consumers is key, Bird says. “These spillovers start with one or two people.
The solutions start with education and awareness. We must make people aware
things are different now. I have learned from working in Sierra Leone with
Ebola-affected people that local communities have the hunger and desire to have
information,” he says. “They want to know what to do. They want to learn.”
Fevre and
Tacoli advocate rethinking urban infrastructure, particularly within low-income
and informal settlements. “Short-term efforts are focused on containing the
spread of infection,” they write. “The longer term – given that new infectious
diseases will likely continue to spread rapidly into and within cities – calls
for an overhaul of current approaches to urban planning and development.”
The bottom
line, Bird says, is to be prepared. “We can’t predict where the next pandemic
will come from, so we need mitigation plans to take into account the worst
possible scenarios,” he says. “The only certain thing is that the next one will
certainly come.”
• This
piece is jointly published with Ensia
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