‘A common germ pool’: The frightening origins of the coronavirus

In November 2002, a 46-year-old man from the Chinese coastal
province of Guangdong developed a fever and struggled to breathe.
Not much is known about him except that he was a local government
official with a wife and daughter. But, as David Quammen writes in
his book
Spillover
, a note in his medical history jumps out: He had
recently helped to prepare meals that included chicken, domestic
cat, and snake.

This man had one of the earliest suspected cases of severe acute
respiratory syndrome, the disease that later became known as SARS.
(Quammen doesn’t report whether he survived.) Like COVID-19, the
pandemic currently sweeping across the globe, SARS was a
coronavirus. And like COVID-19, the disease caused by the new
coronavirus, SARS originally came from animals.

Some 60 percent
of the new diseases that crop up around the globe each year are
zoonotic — meaning they come from domesticated animals or
wildlife. Scientists have found that infectious diseases are now
emerging more
rapidly
than in the past. In the 1950s, some 30 new infectious
diseases were reported over the course of the decade, according to
a study in the
journal Nature. In the 1980s, the number reported jumped to nearly
100. Part of that increase is likely a result of how we are
treating the environment.

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“There seems to be a pretty clear signal that there are more
disease emergence events,” said Aaron Bernstein, interim director
of the Center for Climate, Health, and the Global Environment at
the Harvard School of Public Health. Humans suffered from smallpox
for centuries, but there are also similar diseases in other species
— camel pox, cow pox, monkey pox. If given the opportunity,
diseases can jump, crossing boundaries from one species to
another.

“We swim in a common germ pool with other life forms,”
Bernstein said.

SARS originated in bats, likely by way of the mongoose-like
civet
cat
. The Middle East respiratory syndrome known as MERS also
came from bats and was passed to humans through
camels
. It’s too early to say exactly where COVID-19 began,
but it likely traveled from bats to scaly anteaters
called pangolins
to humans. Such species-to-species spillovers
are common, and to some degree inevitable.

But as people expand into wilderness areas, bringing
urbanization and agriculture, they encroach on species like bats
that originally had free rein and plenty of space to roam.
Proximity gives diseases a better shot at making a cross-species
jump. “We’re becoming an enormously voracious species of 7.5
billion people, and we’re really destroying the natural habitat
of lots and lots and lots of other species,” said Frank Snowden,
a professor emeritus of the history of medicine at Yale University.
“That has enormous health consequences.”

According to a 2017
study
, ebola outbreaks — which have also been linked to bats
— in Central and West Africa were more likely to occur in areas
that had recently been deforested. “The invasion of West African
forests by the palm oil companies destroyed the canopy of the
natural forest,” Snowden said. “And so bats, not having their
natural habitat, had to move to different places — places where
human beings are.”

The issue is compounded at
wildlife markets
in China (and around the world) where live
animals are kept in close proximity to each other and to humans.
Pangolins sit near chickens and snakes; pigs rub shoulders with
foxes and badgers. It’s a perfect breeding ground for zoonotic
diseases, and for the bats that carry them. “[Bats] are mobile
and they’re mammals, so they’re closely related to us,”
Bernstein said. “And they’re losing habitats, so they go to
these markets in search of food.”

Loss of biodiversity can also cause diseases to spread more
widely. As species inch toward extinction, it knocks ecosystems off
balance; remaining creatures
may be more adept at spreading illnesses
. Scientists believe
that West Nile virus, carried by migratory birds,
might have benefited
from a fall in niche bird species like the
woodpecker and a rise in more virus-friendly species like robins
and crows.

Warming temperatures brought on by climate change exacerbate the
problem. As temperatures rise, animals are mixing in new and
unexpected ways — providing even
more opportunities
for diseases to spread.

In reaction to the global COVID-19 pandemic, Chinese authorities
have shut down the local wildlife market in Wuhan where the virus
was likely first transmitted to humans and enacted a
ban
on buying, selling, or eating wild animals. (But the new
ban reportedly leaves
loopholes
for animals used in traditional Chinese medicine.)
Wildlife trade isn’t only a problem in China, and habitat
destruction will surely continue apace. The lesson from coronavirus
may be the same lesson to be learned from climate change — that
the best hope for stability is to preserve the natural systems that
humans depend on for a safe climate, nourishment, and protection
from disease.

According to Quammen, zoonotic diseases serve as a reminder that
people really can’t separate themselves from the natural world,
even by bulldozing nature. It’s there even if you can’t
immediately see it. “Shake a tree, and something falls out,” he
wrote in Spillover. Urbanization, industry, and globalization have
brought many benefits, but they have also increased human
vulnerability to certain types of disease.

Bernstein offered a sobering warning that the coronavirus is not
the worst pandemic possible. “We’ve gotten a few shots over the
bow here,” he said. “We’ve had SARS, MERS, COVID, HIV. We
need to see what nature is trying to tell us here. We need to
recognize that we’re playing with fire.”

This story was originally published by Grist with the headline
‘A common germ pool’: The frightening origins of the
coronavirus
on Mar 18, 2020.

Source: FS – All – Science – News
‘A common germ pool’: The frightening origins of the coronavirus