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Can my sourdough starter spread COVID-19?

Last Updated Jun 4, 2020 at 2:22 pm PDT

Your sourdough starter probably won't act as a vector for the novel coronavirus, experts say. (Courtesy Flickr: JoLynne Martinez)

NEWS 1130 listener worries giving sourdough starter to family and friends could spread coronavirus

Yeast cells are alive but unlikely to carry the virus, experts say

NEWS 1130 is working hard to get you the information you need about the COVID-19 pandemic.

We are responding to your questions in a segment we call NEWS 1130 Gets Answers.


Tina came to us with a somewhat unusual question. She wanted to know whether it’s safe to pass on a sourdough starter to friends and family.

“I’ve tossed many sourdough babies away because I’m concerned that, as an actively fermenting item, it could carry COVID-19,” she said on Twitter.


The first expert contacted by NEWS 1130 did not seem impressed, responding, “You’re kidding right? This is a real question?”

Two other experts, however, seemed less incredulous about Tina’s dilemma. Both agreed Tina’s starters are unlikely to spread the virus, although they interpreted some research involving yeast and the coronavirus differently.

“Great question,” University of Toronto professor of family and community medicine Dr. David White said in an email.

“Sourdough starter contains yeast cells, which is how bread rises. Viruses can infect and live in yeast cells,” he said, citing a report in Nature detailing how researchers used yeast cells to create a synthetic version of the new coronavirus that could be used to study the virus. “So the COVID virus could survive in sourdough starter.”

White said Tina should be safe to pass on new starters as long as she throws out any starter from before she began practising social distancing, as long as she is sure she hasn’t picked up the virus since.

But Sarah Otto, a UBC zoology professor who has studied the evolution of yeast, said it’s “unlikely” for a sourdough starter to carry the virus.

“For COVID to grow on the yeast starter, the virus would need to bind to the yeast’s ACE2 receptor, but yeast are so distantly related to mammals that this is unlikely (one would have to model the binding properties to answer this properly, but the expectation would be a very low match).”

She said the research reported by Nature does not show that the virus can spread from yeast cell to yeast cell. The scientists used “yeast tricks” to copy the coronavirus, but that doesn’t mean yeast can be infected by the virus, she said.

“It would be like the difference between the original Mona Lisa and a photocopy version. Photocopies might be useful to study for some reasons, but they don’t capture the full picture (here the ability for viruses to infect cells),” she said.

Both Otto and White said anyone who receives a sourdough starter should clean the container it comes in and wash their hands to prevent possible transmission of the virus.

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