In the year since seafood hawkers started appearing at
Wuhan’s hospitals sickened with a strange and debilitating pneumonia,
the world has learned a lot about Covid-19, from the way it spreads to
how to inoculate against the infection. Despite these advances, a chasm remains in our
understanding of the virus that’s killed nearly 2 million people and whipsawed the global economy: we still don’t know how it began.
Where
the pathogen first emerged and how it transmitted to humans is a
stubborn mystery, one that’s becoming more elusive with each passing
month. Before the initial cluster among stall-holders at a produce
market in central China, the trail largely goes cold, and the country
the novel coronavirus hit first — the place many blame for unleashing
the disease on an under-prepared world — now has little incentive to
help find the true origin of the greatest public health emergency in a
century.
China has effectively snuffed out Covid-19, thanks to stringent border curbs, mass testing and a surveillance network that allows infected people and their
contacts to be tracked via mobile phone data. With the fight over the
pandemic’s source becoming an extension of the broader conflict between
the world’s two superpowers, China is now trying to revise the virus
narrative from the beginning, and nowhere is that more evident than at
the original epicenter: Wuhan.
The Battle Against Covid-19 Special Exhibition seeks to
memorialize everything from mask-making machines and 2,000-bed temporary
hospitals to lockdown haircuts and remote learning. A timeline at the
entrance to the exhibit chronicles President Xi Jinping’s virus actions
in careful detail, starting on Jan. 7, when he ordered the country’s
leaders to contain the rapidly swelling outbreak and ending in
September, when Xi gave a speech to bureaucrats in Beijing on how China
tamed the coronavirus.
With the virus firmly contained — Wuhan has had no
locally-transmitted cases since May — there’s a growing push to dispel
the idea that China was the ultimate source of the virus, known
officially as SARS-CoV-2. A foreign ministry spokesman has been
espousing theories that link the virus to the U.S. military, and after a
spate of cases in Chinese port and cold storage workers, state-backed
media are claiming the virus could have entered the country on imported frozen food. They’ve also seized on research that suggests there were infections in the U.S. and Italy that pre-date those in Wuhan.
While
some of these theories may have credence, the irony is that we may
never know how and where the virus emerged. China has ignored appeals
for an independent investigation into the virus’s origin, hammering
Australia with trade restrictions after it called for one. It’s also
stalled efforts by the World Health Organization to get top infectious
diseases experts into Wuhan this year. That’s prevented the painstaking
epidemiological detective work — from probing samples of the city’s wastewater, to
checking patient specimens collected months before the outbreak
appeared for early traces of the pathogen and undertaking tests at the
food market itself — that could provide insight into the chain of
events that brought the virus to the bustling capital of Hubei province,
and how to stop it from happening again.
Now, with a WHO team focused on tracing the virus’s origin hoping to visit Wuhan in January, and a crew commissioned by The Lancet medical journal also on the hunt, the city may not have much to reveal.
Life is largely back to normal for Wuhan’s 11 million people, the first
to experience the lockdowns now shuttering parts of Europe and North America for a second time.
“These
things are awfully hard to do retrospectively, even if all the evidence
is still in place,” said Robert Schooley, an infectious-diseases
physician at the University of California, San Diego and editor-in-chief
of the journal Clinical Infectious Diseases.
Located just 5 miles south of the exhibition center, the
Huanan seafood market is partitioned off by eight-foot-high metal
barricades, replete with pictures of tranquil rural scenes — bolted to
the ground. Potted palm trees dot the perimeter of the multi-story
building, site of the world’s first known cluster of Covid-19. Until
government cleaners swooped in in late 2019, to close, vacate and
sanitize dozens of stalls, it was a key source of produce for locals and
restaurants in central Wuhan. It was also reported by
media including Agence France Presse to have sold a range of wild
animals and their meat, from koalas and wolf pups to rats and palm
civets, the cat-like animals suspected of being the conduit of the SARS
virus between bats and humans, which led to a deadly outbreak in China
in 2002 that subsequently spread to other parts of the world.
Now
only eyeglass vendors line the sparsely filled aisles on Huanan’s
second floor, their diminished clientele carefully vetted by security
guards. On a recent visit to the market, Bloomberg News reporters were
warned away by plain-clothes officials and later, police.
In Wuhan Tiandi, a shopping precinct that claims to have China’s first outdoor food street with air conditioning, couples and families rugged up against the
winter chill casually remove their face masks to eat and chat. When
asked about the origins of the virus, most said it didn’t start in the
city.
For all of China’s stonewalling, scientists suspect they could well be right.
The place a virus first infects a human isn’t necessarily where it begins spreading efficiently among people, said Joel Wertheim,
an associate professor of medicine at the University of California, San
Diego, where he studies the evolution and epidemiology of infectious
diseases. HIV, for instance, is thought to have originated in
chimpanzees in southeastern Cameroon, but didn’t begin spreading readily
in people until it reached the city of Kinshasa, hundreds of miles
away.
While researchers surmised early on that the horseshoe bat identified as the likely source of SARS could also have spawned
SARS-CoV-2, how it crossed the species barrier to infect humans remains
unclear. It’s likely that precursors to this virus spilled over from
their natural reservoir many times, but went extinct when infected
individuals didn’t transmit the virus to anyone, according to Wertheim.
Eventually, the virus infected someone who passed it to multiple people,
who also passed it on to others.
“You could have sort of these one-off, dead-end transmission
chains until you get into Hubei province, which is where the
epidemiological data says this is where it was spreading,” Wertheim
said. “And it seems to have seeded the rest of China from there, and
then from China to the rest of the world.”
Chinese scientists
published the genetic sequence of the virus in January, a move that has
allowed experts elsewhere to make some inroads into how this may have
started. Wertheim and his colleagues studied SARS-CoV-2 virus genomes
and the pace at which they mutated and diversified from the earliest
known specimens in Wuhan. From mid-October to mid-November 2019 is the
most plausible period in which the first case in people emerged,
according to a pre-print of Wertheim’s research released Nov. 24.
The
question of how the pathogen got to central China is the subject of
more debate. The coronaviruses most closely related to SARS-CoV-2 were
found in bats in China’s Yunnan province, some 1,000 miles southwest of
Wuhan. The mountainous region borders Vietnam, Laos and Myanmar, all
countries known to have sizable horseshoe bat populations.
“We can’t rule out that the person who first got
this virus was in Yunnan and then infected another person who hopped on a
plane and went back to Wuhan after their vacation,” said Michael Worobey,
head of ecology and evolutionary biology at the University of Arizona
in Tucson, who worked with Wertheim on the timing of the first possible
case.
Other scientists see a potential answer in outbreaks half a world away. Over
the past few months, SARS-CoV-2 has exploded among mink populations in
Europe and North America after the virus was introduced by infected
humans, with which they share some respiratory-tract features. Millions
of the semi-aquatic, carnivorous mammals, reared for their soft pelts,
have been culled to purge the pathogen from farms where they have been
linked to mutations in the coronavirus that some scientists said could pose a threat to vaccine efficacy.
“The
mink scenario to me says, where you’ve got a large population of
susceptible animals in the right conditions with a certain density, then
this virus is just going to go right through it,” said Hume Field, an
Australian wildlife epidemiologist who worked on the international probe
that linked SARS to horseshoe bats and is a member of The Lancet’s
Covid-19 origins task force.
Field discovered the source of a
deadly virus that killed horses and their handlers in eastern Australia
more than 20 years ago. After an exhaustive search, he eventually found
Hendra virus originated in large fruit bats, known locally as flying
foxes. The finding led scientists to understand what veritable virus treasure troves bats are. Besides his investigation into the origins of Hendra and
SARS, Field has also helped trace the Nipah and Ebola Reston viruses
back to bats.
Did
SARS-CoV-2 jump directly from bats to humans, or did it spread to
another animal — a so-called intermediate host — that then passed it on
to people? Finding out is key to reducing the risk of secondary
outbreaks and the emergence of new strains impervious to the Covid-19 vaccines now being rolled out around the world. The virus’s affinity with mink
suggests wild animals from the same “mustelid” family, which includes
weasels and ferrets, that interacted with coronavirus-carrying bats may
have played an intermediary role, according to Field.
Mink resemble “a microcosm of what could have happened prior to Covid,” said Peter Daszak,
a New York-based zoologist who is part of both the WHO and The Lancet
teams trying to trace the virus’s origins. He theorizes that the virus
went from horseshoe bats to people in Wuhan via wildlife that were sold
in the city or people connected with that trade. In the wake of the
outbreak, China said it curtailed the sale and consumption of wild animals, but the trade is difficult to
police given how integral it is to cuisine and traditional medicines,
particularly in the south.
Since
bats don’t fly regularly from southern China to Wuhan, it’s more likely
the virus was propagated in civets or other susceptible animals raised
on farms for sale in the Huanan market, Daszak said. In the wild,
coronaviruses spread across animal species via the fecal-oral route,
such as when a civet eats fruit contaminated by bat droppings.
“We
still don’t really know what animals were present in that market in the
beginning,” he said. “It’s quite possible there are other animals in
China that were infected.”
Finding out more from those who were there will be difficult, especially a year on. Scientists still don’t know the precise source of the Ebola virus, for example, nor how the H1N1 influenza virus that swept the world in 2009 jumped from pigs into people. It’s
possible the origin of Covid-19 will never be found, George Gao, the
director of China’s Center for Disease Control and Prevention, told the Xinhua news agency this week. “We looked for suspect animals in Wuhan, but found none.”
After
the Huanan market was closed, some of its stallholders were relocated
to the cavernous Sijimei food market on Wuhan’s northern outskirts. On a
frigid day in mid-December, it was almost deserted of customers, but
few vendors were willing to speak to Bloomberg about the events that
took place 12 months earlier. A spice and condiment seller who said his
family name was Xie, confirmed he’d moved from Huanan in March, but said
he couldn’t remember anything that happened there. Shortly after,
security guards appeared saying that foreign media were barred from
filming.
The response was similar at a nearby open-air market, where other
Huanan vendors had set up stalls. An attendant selling lamb carcasses
confirmed the business moved there in March before he was told to shut
up by his manager. Moments later, two guards appeared, saying any
interviews should be cleared by the Communist Party.
Bloomberg has
made multiple requests over the course of 2020 to interview key Chinese
scientists, including both the director and chief epidemiologist at the
country’s CDC, and the nation’s most experienced coronavirus expert,
Shi Zhengli.
Shi
— known as China’s “bat woman” for her intrepid, decade-long
exploration and collection of viruses in bat-festooned caves — has been
at the center of speculation about the source of SARS-CoV-2 since its
first weeks. She operates a laboratory at the Wuhan Institute of
Virology that studies some of the planet’s worst infectious disease
threats. Its location in a peri-urban industrial area about 20 miles
from the Huanan market has fueled theories that the virus either
accidentally escaped from the lab or, more sinister, that it was
genetically engineered and deliberately released.
Shi has said the genetic characteristics of the viruses she’s worked on don’t match SARS-CoV-2 and told the state-run China Daily newspaper in early February that she was willing to “bet my life” that the outbreak had “nothing to do with the lab.” Shi is also open to “any kind of visit” to rule it out, the BBC reported Dec. 22.
Still,
in a vacuum of information, conspiracy theories have taken hold, with
President Donald Trump — who has repeatedly referred to SARS-CoV-2 as
the “Chinese virus” — a proponent of the lab hypothesis. He said as
early as April that China may have “knowingly” unleashed the pathogen, and the U.S. has criticized the country’s lack
of cooperation on tracing its source. For its part, China defends its
work with the WHO. It’s engaged with the body on origin-tracing in a
``transparent’’ manner and WHO experts have been allowed to visit the
country, Wang Wenbin, a foreign ministry spokesman, told reporters this
month.
Field, who’s also a science and policy adviser for
EcoHealth Alliance, a New York-based nonprofit that works to prevent
viral outbreaks around the world, said it’s possible Chinese scientists
are well advanced in their investigations, but fears any findings into
how the virus originated — whether from China or elsewhere — will be
clouded in “conspiracy cover-up talk.”
“How do we make those broadly accepted to what now seems to be quite a cynical and politicized audience?”
It will likely require a level of openness China is showing no signs of embracing.
On
a recent visit to the Wuhan Institute of Virology, security staff tried
to stop a Bloomberg journalist from taking photographs and video from a
public road outside. One guard stood in the way of the car until police
arrived. Multiple requests to visit the infectious diseases lab were
denied.
Yang
Feng, a 51-year-old retiree, said she found the exhibit cathartic, a
reminder of everything her home town had been through, from the almost
three-month lockdown to the 3,869 people who died. “I wanted to recap
the history,” she said. “Now, you can’t tell Wuhan is a city that’s been
through the virus.”
But Yang shakes her head when asked where she thinks Covid-19 originated.
“I don’t know,” she said. “I really don’t know.”
—Jason Gale, Emma O’Brien and Claire Che