|
 China has dismissed as "ridiculous" a Harvard Medical School study
that suggested the disease could have been spreading throughout the
country as early as last August, taking pains to deny claims that it
tried to cover up the initial outbreak.
Many scientists say the study's design was unhelpful, but they still
question Beijing's official account of when the disease first
emerged.
Published in April, Beijing's timeline shows that cases of "a new
type of pneumonia" were first detected in the central city of Wuhan
late in December and that a new strain of coronavirus was identified
on Jan. 7.
WHAT ARE SCIENTISTS SAYING ABOUT THE ORIGINS OF COVID-19?
The Harvard Medical School study, published on June 9, used
satellite imagery of Wuhan parking lots to show a spike in hospital
visits beginning as early as August 2019, four months before the
outbreak officially began. It also identified a surge in
search-engine queries for "cough" and "diarrhea" in August.
Its authors said they were still investigating the viability of the
data and conceded there could be alternative explanations for the
increases.
However, several other studies have used genetic analysis of
SARS-CoV-2 to show the virus could have emerged far earlier and
caused more deaths than Beijing has said, and might have been
circulating for months before authorities took action on Jan. 23.
Some also question the consensus that the virus crossed the species
barrier in Wuhan, possibly via bats or other animals on sale at the
Huanan seafood market, where the pandemic is believed to have
started.
With little surviving evidence from the market, which was shut down
and cleaned up early in the outbreak, other studies say the virus
might not have originated in Wuhan at all.
A paper released in May by the Broad Institute, a U.S. research unit
with ties to Harvard, said the new virus was already "pre-adapted to
human transmission" when first identified by Chinese health
officials in Wuhan in December, suggesting it had already been
circulating in people.
The researchers said genetic samples of the virus taken from a
Chinese patient in December appeared to have already evolved in a
human environment, and resembled those collected during the latter
stages of the SARS outbreak in 2002 and 2003.
[to top of second column] |
Further, samples from the seafood market were identical to those found in
patients, suggesting they originated in human, rather than animal, sources.
DID THE NEW CORONAVIRUS ORIGINATE IN A WUHAN LAB?
Rather than emerging fully formed in Wuhan, the coronavirus could have been
spreading elsewhere before experiencing a "bottleneck event" in the city, the
Broad Institute paper showed.
Some studies have suggested that insertions in the spike protein on the virus
surface, which allows it to bind to a receptor on a human cell, made it uniquely
suited to human transmission.
That prompted accusations that the virus might have engineered in a laboratory
and accidentally released - suggestions that have been firmly denied by the
Wuhan Institute of Virology, the lab at the center of the allegations.
The majority of virologists and infectious disease experts say the new virus is
most likely to have evolved naturally.
COULD THE NEW CORONAVIRUS HAVE ORIGINATED OUTSIDE WUHAN?
One of the Wuhan lab's senior scientists, Yuan Zhiming, told Reuters in April
that there were still questions to be asked about the origins of the pandemic.
He pointed to studies showing that the SARS-CoV-2 variant circulating in the
United States was a more "primitive" version of the one in China, showing it
might have first emerged there.
Other countries are also reappraising pneumonia deaths before last December to
check if COVID-19 was the cause.
A study published last month suggested a man in France was infected as early as
Dec. 27, a month before the country's first confirmed cases were reported.
Italian researchers are also weighing the possibility that a higher than usual
number of cases of severe pneumonia and influenza in Lombardy in the last
quarter of 2019 shows the virus arrived earlier than previously thought.
(Reporting by David Stanway; Editing by Kate Kelland, Stephen Coates and
Clarence Fernandez)
[© 2020 Thomson Reuters. All rights
reserved.] Copyright 2020 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
Thompson Reuters is solely responsible for this content. |
