TORONTO -- Despite new reports that U.S. officials are investigating the possibility the coronavirus was secretly manufactured in a Chinese lab, there is no scientific evidence to support those theories.

Scientists who’ve studied the virus have already dispelled those rumours and instead pointed to bats as the likeliest source, suggesting that COVID-19 was created by nature, not humans.

At its molecular level, the virus’s genetic makeup closely resembles one that already exists in horseshoe bats in China’s Hunan province. The discovery, which is backed up by several independent studies, isn’t entirely surprising. Bats have an unusually high capacity to harbour viruses and have been linked to past outbreaks, including SARS, MERS and Ebola.

Scientists believe the virus may have spread from bats to an intermediary animal -- possibly stray dogs, snakes or pangolins -- before infecting humans. The fact that the earliest cases of COVID-19 were linked to a live animal market in Wuhan that sold exotic species only bolsters this research.

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More directly, a team of American, British and Australian researchers have flat-out dismissed the notion that the virus was somehow manufactured in a lab.

A paper published last month in the journal Nature Medicine found that the virus, when tested by computer simulations, does not appear to bind well to human cells. The researchers determined that if someone wanted to create a dangerous virus capable of spreading among humans, their own simulations would show that this virus simply wouldn’t work.

"Our analyses clearly show that SARS-CoV-2 is not a laboratory construct or a purposefully manipulated virus," researchers wrote in the article.

Unsubstantiated online rumours, which started on fringe websites and have been fanned by U.S. politicians such as the Republican Senator from Arkansas, Tom Cotton, point out that Wuhan is home to a high-security infectious disease lab that has studied coronaviruses and bats.

U.S. Secretary of State Mike Pompeo has publicly speculated about the lab’s proximity to the Wuhan market in an interview with Fox News.

"We know that there is the Wuhan Institute of Virology just a handful of miles away from where the wet market was," Pompeo said Wednesday. The institute is located about 13 kilometres from the market.

U.S. officials told The Associated Press that the American embassy in Beijing flagged concerns about potential safety issues at the Wuhan lab in 2018, but stressed there is no evidence that the virus originated there nearly two years later.

CTV News Science and Technology specialist Dan Riskin said it’s not unusual that the lab would conduct such research. China has been studying coronaviruses and bats ever since the SARS outbreak of the early 2000s.

“I think it shows us that the scientists knew this was coming. Of course they were studying bats. Of course they were studying coronaviruses. People have been screaming at the top of their lungs for years that a coronavirus outbreak is coming,” Riskin told CTVNews.ca, pointing out past outbreak warnings from former U.S. President Barack Obama, National Institute of Allergy and Infectious Diseases director Anthony Fauci and former U.S. President George W. Bush.

“It’s not because they were planning to unleash it on humans. It’s because they were trying to save us.”

THE POLITICAL ANGLE

Even top U.S. intelligence officials have cast doubt on the theory that the virus is manmade.

On Tuesday, the Pentagon’s top general, Gen. Mark Milley, said the U.S. looked into the possibility that COVID-19 was manufactured in a lab after noticing “a lot of rumours and speculation.”

“A lot of intelligence” has looked into the theory, Milley said, and found that “the weight of evidence” sides with scientists who say the virus began naturally.

However, Milley didn’t go so far as to offer a definitive answer.

“We don’t know for certain,” he said.

On Wednesday, one day after the top general’s comments, U.S. President Donald Trump was asked about a potential theory, first reported by Fox News citing multiple unnamed sources, that patient zero was a worker at a Wuhan lab who spread the virus to the general population.

CNN later reported a version of the story, suggesting that U.S. officials are probing the possibility, but that it’s too soon to make any conclusions.

"More and more we're hearing the story...we are doing a very thorough examination of this horrible situation,” Trump said of the reports.

The U.S. has suffered the highest COVID-19 death toll in the world and has the highest number of cases, and Trump -- who has dubbed the virus the “Chinese virus” -- has repeatedly blamed China for the outbreak.

Earlier this week, Trump accused the WHO of failing to “call out China’s lack of transparency” in the early days of the outbreak and cancelled billions of dollars’ worth of funding for the UN health agency.

Wayne Petrozzi, a professor emeritus of politics at Ryerson University, said there are legitimate reasons to be skeptical of China’s response. Reports have suggested that the Chinese government censored certain words from social media at the beginning of the outbreak, and, in the early 2000s, China infamously covered up the SARS outbreak, going so far as to hide patients from WHO investigators.

Petrozzi said it’s important not to conflate real concerns about China’s lack of transparency with unsubstantiated rumours that the virus was manufactured by humans.

“It is a problem that is separate and apart from some nonsense conspiracy theory about some biological weapon mistakenly escaping from a lab,” he said.

On Thursday, U.S. Defence Secretary Mark Esper dismissed rumours that the virus came from a lab. In an interview with NBC’s “Today” show, Esper said he doesn’t have much faith in China being transparent about the outbreak, but "a majority of the views right now is that it is natural, it was organic.”

So far, Trump has not outright accused China of manufacturing COVID-19 in a lab. But with the president facing re-election this fall, Petrozzi said he’s concerned that the blame for the virus will be increasingly pegged on China — a country Trump repeatedly slammed during the 2016 campaign.

“It will only get worse, because what is there for him to lose?"

Chinese scientists have said that the virus originated at the wet market in Wuhan. But some Chinese politicians have floated their own unsubstantiated rumour, suggesting that the virus originated in the U.S. and was somehow brought into China, possibly by the American military.

Lijian Zhao, a spokesperson for China’s foreign ministry, has tweeted a report that purported to offer “further evidence” that the virus started in the U.S. The report was published on a website filled with falsehoods, including conspiracy theories about 9/11.

With files from The Associated Press

Edited by CTVNews.ca Producer Michael Stittle