Tag Archives: bats

What we know about the origins of COVID-19

By Deborah J. Nelson

(Reuters) -Scientists are revisiting a central mystery of COVID-19: Where, when and how did the virus that causes the disease originate?

The two prevailing competing theories are that the virus jumped from animals, possibly originating with bats, to humans, or that it escaped from a virology laboratory in Wuhan, China. The following is what is known about the virus’ origins.

WHY IS THE LAB IN WUHAN A FOCUS OF INTEREST?

The Wuhan Institute of Virology (WIV) is a high-security research facility that studies pathogens in nature with the potential to infect humans with deadly and exotic new diseases.

The lab has done extensive work on bat-borne viruses since the 2002 SARS-CoV-1 international outbreak, which began in China, killing 774 people worldwide. The search for its origins led years later to discovery of SARS-like viruses in a southwest China bat cave.

The institute collects genetic material from wildlife for experimentation at its Wuhan lab. Researchers experiment with live viruses in animals to gauge human susceptibility. To reduce the risk of pathogens escaping accidentally, the facility is supposed to enforce rigorous safety protocols, such as protective garb and super air filtration. But even the strictest measures cannot eliminate such risks.

WHY DO SOME SCIENTISTS SUSPECT A LABORATORY ACCIDENT?

To some scientists, the release of a dangerous pathogen via a careless lab worker is a plausible hypothesis for how the pandemic started and warrants investigation. The Wuhan lab, China’s leading SARS research facility, is not far from the Huanan Seafood Market, which early in the health crisis was cited as the most likely place where animal-to-human transmission of the virus may have taken place. The market was also the site of the first known COVID-19 super spreader event. Their proximity raised immediate suspicions, fueled by the failure so far to identify any wildlife infected with the same viral lineage and compounded by the Chinese government’s refusal to allow the lab-leak scenario to be fully investigated.

Scientists and others have developed hypotheses based on general concerns about the risks involved in live virus lab research, clues in the virus’ genome, and information from studies by institute researchers. Although the Wuhan lab’s scientists have said they had no trace of SARS-CoV-2 in their inventory at the time, 24 researchers sent a letter to the World Health Organization (WHO) urging a rigorous, independent investigation. The WHO’s first such mission to China this year failed to probe deeply enough, they wrote.

A U.S. State Department fact sheet, released before the WHO mission in the waning days of the Trump Administration, alleged, without proof, that several WIV researchers had fallen sick with symptoms consistent with COVID-19 or common seasonal illnesses before the first publicly confirmed case in December 2019.

A May 5, story by Nicholas Wade in the Bulletin of the Atomic Scientists, said lab scientists experimenting on a virus sometimes insert a sequence called a “furin cleavage site” into its genome in a manner that makes the virus more infective. David Baltimore, a Nobel Prize-winning virologist quoted in the article, said when he spotted the sequence in the SARS-CoV-2 genome, he felt he had found the smoking gun for the origin of the virus.

WHAT ARE THE ARGUMENTS FOR ANIMAL-TO-HUMAN TRANSMISSION?

Many scientists believe a natural origin is more likely and have seen no scientific evidence to support the lab leak theory. Kristian G. Andersen, a scientist at Scripps Research who has done extensive work on coronaviruses, Ebola and other pathogens transmissible from animals to humans, said similar genomic sequences occur naturally in coronaviruses and are unlikely to be manipulated in the way Baltimore described for experimentation.

Scientists who favor the natural origins hypothesis have relied largely on history. Some of the most lethal new diseases of the past century have been traced to human interactions with wildlife and domestic animals, including the first SARS epidemic (bats), MERS-CoV (camels), Ebola (bats or non-human primates) and Nipah virus (bats).

While an animal source has not been identified so far, swabs of stalls in the wildlife section of the wildlife market in Wuhan after the outbreak tested positive, suggesting an infected animal or human handler.

HAS NEW INFORMATION EMERGED TO LEND CREDENCE TO ONE THEORY OVER ANOTHER?

The scientists’ March 4 letter to the WHO refocused attention on the lab-leak scenario, but offered no new evidence. Nor has definitive proof of a natural origin surfaced.

U.S. President Joe Biden on May 26 said his national security staff does not believe there is sufficient information to assess one theory to be more likely than the other. He instructed intelligence officials to collect and analyze information that could close in on definitive conclusion and report back in 90 days.

(Reporting by Deborah J. NelsonEditing by Bill Berkrot)

COVID may have taken ‘convoluted path’ to Wuhan, WHO team leader says

By Josh Horwitz and David Stanway

WUHAN, China (Reuters) – The head of a World Health Organization-led team probing the origins of COVID-19 said bats remain a likely source and that transmission of the virus via frozen food is a possibility that warrants further investigation, but he ruled out a lab leak.

Peter Ben Embarek, who led the team of independent experts in its nearly month-long visit to the Chinese city of Wuhan, where the outbreak first emerged at a seafood market in late 2019, said the team’s work had uncovered new information but had not dramatically changed their picture of the outbreak.

“The possible path from whatever original animal species all the way through to the Huanan market could have taken a very long and convoluted path involving also movements across borders,” Embarek told a nearly three-hour media briefing.

Embarek said work to identify the coronavirus’s origins points to a natural reservoir in bats, but it is unlikely that they were in Wuhan.

Investigators were also looking for Chinese blood samples that could indicate that the virus was circulating earlier than first thought, he said.

“In trying to understand the picture of December 2019 we embarked on a very detailed and profound search for other cases that may have been missed, cases earlier on in 2019,” he said.

“And the conclusion was we did not find evidence of large outbreaks that could be related to cases of COVID-19 prior to December 2019 in Wuhan or elsewhere.”

The possibility the virus leaked from a lab – which has been the subject of conspiracy theories – was extremely unlikely and did not require further study, Embarek said.

Liang Wannian, head of China’s expert panel on the outbreak, said there was evidence of coronavirus infections that could have preceded the first detected case by “several weeks”.

“This suggests that we cannot rule out that it was circulating in other regions and the circulation was unreported,” he told the briefing.

FROZEN ANIMALS?

Embarek said the team had identified market vendors selling frozen animal products including farmed wild animals.

“So there is the potential to continue to follow this lead and further look at the supply chain and animals that were supplied to the market,” he said.

China has pushed the idea that the virus can be transmitted by frozen food and has repeatedly announced findings of coronavirus traces on imported food packaging.

“We know the virus can survive in conditions that are found in these cold, frozen environments, but we don’t really understand if the virus can transmit to humans” or under which conditions, Embarek told the briefing.

The team arrived in Wuhan on Jan. 14 and after two weeks of quarantine, visited key sites including the Huanan seafood market, the location of the first known cluster of infections, as well as the Wuhan Institute of Virology, which has been involved in coronavirus research.

Members of the team sought to rein in expectations for the mission, with infectious disease expert Dominic Dwyer saying it would probably take years to fully understand the origins of COVID-19.

The United States said China needed to be more open when it comes to sharing data and samples as well as allowing access to patients, medical staff and lab workers. Beijing subsequently accused Washington of politicizing a scientific mission.

(Reporting by Josh Horwitz in Wuhan and David Stanway in Shanghai; Additional reporting by Stephanie Nebehay in Geneva; Writing by Tony Munroe; Editing by Raju Gopalakrishnan, Gareth Jones and Nick Macfie)