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We Still Don't Know Where Covid-19 Came From

We Still Don't Know Where Covid-19 Came From

Wednesday, 13 January, 2021 - 05:30

People want to know where the coronavirus came from. If humans first caught it from bats, then where and how? Did Covid-19 escape from a lab, as several magazine articles have insinuated? While most scientists dismiss a deliberate release of the virus as a conspiracy theory, they can’t completely dismiss the possibility that it escaped by accident.


International investigations could shed light on the matter, but they’ve gotten off to a bumpy start. A WHO investigative team was held up for months before finally getting admitted to China this week. Another team associated with the Lancet has yet to start field work there. Getting to the bottom of things is not only critical for preventing future pandemics, it’s important for keeping the public in the loop, to keep people motivated to help mitigate the spread.


“I think we all feel that more work should be done in China on trying to find the origins,” says UC Berkeley geneticist Rasmus Neilsen, who has been trying to piece together how SARS-CoV-2 evolved. “I think we all feel that would benefit science.”


One problem, he says, is the spread of conspiracy theories that Covid-19 was created in a lab and then intentionally released. “I think that has really harmed the case for a proper investigation.” While investigating a lab-accident origin is important, he says, it’s gotten lumped in with tinfoil hat ideas.


He says the Chinese government has also thrown up barriers. “There certainly hasn't been openness.” The fact that a WHO team finally got into the country does not mean they will get the kind of access they need.


He and other scientists I interviewed say ideally investigators should be able to collect environmental samples from different parts of China, including areas inhabited by bats known to harbor genetically similar coronaviruses. (The closest-related viruses have previously been found in bats living hundreds of miles from Wuhan.)


That could help them track down the virus’s origin, despite the delay in getting access to China. Neilsen says mutations in coronaviruses crop up at a steady enough rate to work as a sort of molecular clock. Taking advantage of this, he’s been able to show that SARS-CoV-2 diverted from the most closely related known bat viruses 51 and 37 years ago. They’ve been evolving in different directions ever since.


Researchers also need to get access to medical samples from patients. Banked blood and other samples could reveal when the virus first started circulating in humans. Finally, he says, they need to get into the Wuhan Institute of Virology, which houses the world’s largest collection of bat coronaviruses, to study samples, lab notebooks and other records. (Officials at the lab have flatly dismissed the “lab accident” hypothesis.)


Lab accidents have released viruses in the past, says David Sanders, a Purdue University virologist. One led to an outbreak of influenza in 1977. This version of the flu was genetically identical to a strain from the 1950s, he says, “and it almost certainly came from a lab.” He says a likely origin was a Siberian lab called Vector. The Ebola virus leaked from that same lab in 2004. “In the Vector lab that I inspected in Siberia, one of the workers infected herself and then was allowed to go home and, like, gather her stuff up — and then she eventually died.”


One of the mysteries that remains unsolved is how a bat virus got to be so well-adapted to being transmitted between humans. Most bat viruses are not particularly adapted to spread in humans, says microbiologist Stanley Perlman of the University of Iowa, who has studied coronaviruses for years and is a member of a SARS-CoV-2 investigative team organized by the Lancet. That’s one reason two previous epidemic coronavirus diseases he’s studied — SARS, which broke out in 2003, and MERS, or Middle Eastern Respiratory Syndrome — fizzled out.


One explanation he favors is that Covid-19 spread to humans long before it was noticed, becoming better adapted to infecting our species. Since the virus is not particularly harmful in most young people, a low level of SARS-CoV-2 could have been circulating for months. He says clues could come from banked blood and other medical samples, which have been used to suggest the virus had already reached Europe in late 2019.


He agrees that ideally his team and the one from the WHO should have full access to medical samples and the Wuhan Institute of Virology. He also agrees that so far, China has not been transparent — but points out that US has played a part in straining relations, in part by yanking US CDC workers from China once the pandemic began.


The Wuhan Institute of Virology not only houses the world’s biggest collection of bat coronaviruses, they also do research that involves altering those viruses, possibly to make them more transmissible in humans, biologist Richard Ebright of Rutgers University, a longstanding opponent of biological weapons proliferation, told me via email. This “gain-of-function” research doesn’t require genetic engineering. Scientists can use forms of selective breeding to make viruses more transmissible in different species. They do this by infecting or “passaging” the virus through different animals or human cell cultures, selecting for mutations that are more likely to infect us. He says gain-of-function research is not justifiable, but others say it’s valuable for vaccine research as well as learning more about how new viruses get into humans.


Neilsen, the geneticist from Berkeley, says there’s also the possibility that we got this pandemic through bad luck — that a bat virus just happened to have features that made it very bad for people. “There are millions of viruses out there and the one time where we get a pandemic like this that would be that one virus that just happened to have the right mutations to be virulent enough,” he says.


And yes, he says, it’s not tinfoil hat stuff. “This virus has affected us all so much. And so we all want to know as much as we can about the origins, right? Also, to make sure that we minimize the risk of something like this happening again.”


Bloomberg


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