Thursday, October 28

The “Swiss cheese” strategy to protect you from the coronavirus


Comparing the coronavirus to a Swiss cheese might seem trivial, but for the New Zealand virologist Ian M. Mackay it is the perfect analogy of how to protect ourselves against it.

“No isolated prevention measure that we try to implement to combat covid works 100%”, but when “we begin to put together different layers (measures) we create a barrier to prevent that risk,” he tells BBC Mundo.

In his infographic, Mackay shows how each slice of Swiss cheese (measure) has its holes (imperfections)and how combining them can result in greater protection against the virus.

“We know, for example, that masks are useful, but by themselves they are not enough ”, points out the scientist. “Vaccines will be great news, but even when the first one arrives – sometime next year – it will not solve the pandemic by itself.”

It is vital to consider all the layers (measurements) instead of just one. And each of them has its complexities. For example, not all masks are equally effective or are used properly, so each of them has several holes or imperfections ”.

According to the graph Mackay proposes, social distancing is the most important measure because it is “the key to stopping the spread of the virus.”

“A respiratory virus cannot spread between two people who are very far away. The other layers can vary in order depending on the circumstances ”, says the scientist.

Swiss cheese graphic to combat covid

In addition to physical distancing (which includes the precaution of staying home if you get sick), Mackay emphasizes the use of masks, hand hygiene and covering when coughing, limiting time in crowded spaces, quarantining or having a ventilation system or air filtration (in closed spaces).

It is also observed A line that goes through the holes in each slice, what does it mean?

“It means that multi-layered imperfections can add up and let the virus pass — in different situations — so multiple measures must be implemented to reduce risk. The more layers, the easier it will be to cover those holes ”, responds the virologist.

“If there are several people in a room close enough to each other but the room is well ventilated, they have fewer chances of contracting the virus than if there is no ventilation.”

“By implementing multiple interventions, you really increase the chances of there being the lowest possible risk of the virus spreading“.

Cumulative effect

The Swiss cheese model was originally proposed in the 1990s by James T. Reason, a researcher at the University of Manchester (UK), to explain why failures and accidents occur in complex systems.

It is actually a method of risk analysis and management it has nothing to do with respiratory infections and is widely used in sectors such as aviation, engineering and healthcare.

It is also known as the cumulative effect model.

Mackay, who in addition to being a researcher is an adjunct professor at the Faculty of Medicine at the University of Queensland (Australia), believes that Reason’s hypothesis can serve as “an evolving model and a very good way to show how to reduce risks.” to SARS-CoV-2, the virus that causes covid.

It is a model that can also be applied in other viruses that cause respiratory diseases.

“Due to the structure of our societies and the habits to which we are used, it is inevitable that a respiratory virus pandemic will affect many people, even with a vaccine. What is certain is that the more measures we adopt, the better ”, he assures.

Swiss cheese
Masks alone are not enough, but they can provide a “layer” of protection. (Christoph Hetzmannseder / Getty Images)

Individual and shared responsibility

In his chart (updated October 24) Mackay distinguishes between the strategies of individual responsibilityand shared, since some actions can be applied at an individual level (what you can do, such as putting on a mask) or community (what governments implement, how to establish confinements).

One of the most important “layers” for Mackay within the level of “shared responsibility” is that which has to do with information and messages from governments when communicating their measures.

“The disinformation it is a growing problem in the world and we need to take it seriously. Some people do not think it is serious, but I think it is a growing problem, especially due to the use of social networks, “he tells BBC Mundo.

“Some theories (without scientific evidence) can be propagated on the internet by many people and erode any of those layers because they change what people think about masks and other elements,” says Mackay.

The scientist also stresses that if there are mandates by governments that, for example, require wearing a mask, maintaining social distance or avoiding travel, it is important to comply with them. “Doing so is vital for the fight against the disease to be effective,” he concludes.

Ian M. Mackay
Ian M. Mackay is a virologist and professor at the University of Queensland School of Medicine in Brisbane, Australia. (Photo: Infection Prevention Strategy (TIPS))


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