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This Swiss cheese analogy can help protect you from the coronavirus (COVID-19)

More protection measures means less chance of exposure

DETROIT – Can a stack of Swiss cheese help protect you from the coronavirus (COVID-19)? Physically, it cannot. But an analogy based on the cheese actually can, experts say.

Public health officials said the “Swiss cheese” approach to reducing the risk of being infected can help keep people safe.

Some people believe there’s no point wearing a mask because some particles can still get through. Others say social distancing alone is enough to keep them safe, as if there’s an invisible forcefield around them.

But those arguments are full of holes.

“There’s no perfect prevention right now, but multiple imperfect things can still make meaningful reductions in the risk,” said Ryan Malosh, a research scientist at the University of Michigan School of Public Health.

Malosh said our ability to prevent the spread of COVID-19 depends on layering those imperfect protections on top of each other. That’s where Swiss cheese comes in.

“Each intervention that we currently have for COVID-19 prevention is kind of like a slice of Swiss cheese,” Malosh said. “There are holes in it, and so the virus can get through in certain ways.”

But if you layer multiple prevention practices on top of one another, it’s less likely the holes in every slice of cheese will align to make a clear path through the entire stack.

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“The holes are not necessarily aligned in the same places on each slice,” Malosh said. “So if we stack those things up, then we have suddenly a block of cheese that the virus can’t get through.”

Layering imperfect protection measures is something people do all the time. Speed limits control how fast drivers move. Intersections are engineered for safety. Seat belts help restrain passengers in a crash. Air bags help minimize injuries to heads and upper bodies.

None of those driving protections are perfect, but together, they greatly decrease the risks associated with being on the road.

“Wearing a mask or washing your hands or disinfecting surfaces that are being touched more,” Malosh said. “Staying six to 10 feet away from each other -- those things are all good things to think about, but none of them are going to be perfect on their own, so if we can sort of stack those things on top of each other, we can hopefully make a meaningful reduction in our risk.”

Malosh credits the Swiss cheese analogy to Dr. Arnold Monto, a world-renowned expert on influenza at the U of M School of Public Health.

The more layers of Swiss cheese you have, the less likely a hole shows all the way through. This is also an approach business owners can use as they look at reopening. They can think about the potential holes in any of their safety measures and find other steps that cover those holes.


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