PHILADELPHIA (KYW Newsradio) — Almost a year and a half into the coronavirus pandemic, we still don’t know the origin of the virus that causes COVID-19.
It has been widely circulated that the virus likely came from bats, either directly or through an intermediate host animal. That’s what happened in the 2003 SARS outbreak in China and the 1012 MERS outbreak in Saudi Arabia, explains University of Pennsylvania virologist Susan Weiss.
Weiss, who has been working with coronaviruses for 40 years, says most evidence from this pandemic suggests that the virus that causes COVID-19 is zoonotic like SARS and MERS, meaning it is transferrable between animals and people.
"Twice we’ve had viruses from bats to intermediate species to humans. It would be the default belief," Weiss said.
One early theory that was initially rejected has resurfaced recently.
There is another theory that has been around from the beginning: that, rather than jumping from bats to other animals and eventually humans, the virus escaped from the Wuhan Institute of Virology, where it had been manipulated to be super-contagious.
The theory has been on the fringe, but it has gained some traction since the publication of a couple of articles in science publications that are not peer-reviewed.
"I really don’t go for that theory," Weiss says.
She has even tried to manipulate a coronavirus.
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"What we found is you can’t fool Mother Nature. You make something, and then it may not behave the way you think it will," she said.
Weiss says everything about the virus looks to her as if it naturally evolved, as previous coronaviruses have.
"Only natural selection can select a virus that’s so good," she said. "And the fact that we’re getting all these variants — that says that it’s actually adapting to be more able to spread among humans."
A colleague at Penn, Drew Weissman, who developed the mRNA technology used in the COVID-19 vaccines manufactured by Pfizer and Moderna, says he sees other holes in the theory. For one thing, he doubts the possibility of an "escape" from a secure lab.
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"You’re completely protected," he said of the lab's setup. "There’s an anteroom, where you get dressed and undressed. The procedures are set up so that things like that can’t happen."
Scientists continue to investigate both theories. Neither has been proven, but Weiss and Weissman say they find the escape theory highly unlikely.