Nina Wildflower Profile picture
Oct 11, 2024 22 tweets 7 min read Read on X
Some people asked me how I got COVID when I wear an FFP3 to teach.

So I thought I'd revisit "The Swiss Cheese Model" to explain. A🧵

As the diagram shows, it involves firing lasers at cheese.

The cheese blocks the beams. The more layers, the fewer lasers get through. Representation of the "Swiss Cheese Accident Model"
Incidentally, I was taught by Professor James Reason, the originator of the model, when I was an undergraduate.

Many years ago.

If someone is trying to prevent accidents, then a good principle is to use "Lasered Protections". Copy of "Human Error" by James Reason
Of course someone on YouTube has made a video of what happens when you repeatedly fire lasers at cheese.

You can use it to understand UK policy on COVID safety in schools and hospitals.

If I were a scaremonger, I might say "this is your brain after a COVID infection".

I'm not. Screengrab of YouTube video from the University of Stuttgart, which involves firing a laser beam at some cheese.
I did once work as a cheesemonger.

Sainsbury's deli - aged 16-19.

I wore a straw hat. It's when I first realised that perhaps the PPE that workplaces provide might not be appropriate.

We have good cheese in the UK. Stewart Lee "All the cheeses" T-shirt.
Sorry, "Layered Protections".

Respirator masks are brilliant. I've been teaching in them since 2021 and nothing has got through my mask at school.

My children wear them too.

But that's the only protection they get. We think COVID got around, rather than through their masks. Teacher wearing FFP3 mask.
Back to the lasers!

If you pause the video, it's possible to find the exact moment the cheese gets hit with the laser.

But that's not how the Swiss-Cheese-Model-of-Accidents-applied-to-COVID works.

Instead, play the video normally, and hit "screenshot". Screengrab of cheese being melted by a laser, clearly taken from YouTube.
1st exposure

Sick child in my class.

Ok, didn't get hit by the laser!

The COVID protection used worked to prevent infection.

Great news. Cheese melted by laser.
2nd exposure

Sick colleague.

Didn't get hit by the laser either!

These masks work really well!

Even when children use them. Cheese melted by laser.
3rd exposure

Sick child in a colleagues class, but I used the room after them. #CovidIsAirborne and you can catch it from someone who was in the room before you arrived.

The mask worked. Cheese melted by laser.
4th exposure.

This is not meant to be funny. I'm not doing call-backs or anything.

Sick child in my son's class.

His mask worked. Cheese melted by laser.
I'm just doing random screenshots. It took me about a minute to do all of them.

This is some cheese that's been melted by laser.

All the cheeses. Cheese being melted by laser.
5th exposure.

This was a close call. My son's friend came in with active Covid. My son had the presence of mind to lend him a mask.

2 less-than-perfect masks will stop COVID. Cheese melted by laser.
6th exposure

Me again. Another sick child in my class.

The mask worked. Again. Cheese melted by laser.
7th exposure.

Presymptomatic child in my son's class.

The parents have COVID. They sent the child in anyway.

The mask works. Cheese melted by laser.
If you are starting to see a problem with this model, we aren't done yet. Swiss cheese model
8th exposure.

My son's school. The child was sick, but "their attendance is already too low" and they are forced into school.

Still, the mask worked. Cheese melted by laser.
The next week, just due to chance, neither my sons nor I meet anyone with Covid.

Even though we are all in school.

This happens sometimes.

It's a school, not a COVID ward.

We are not constantly exposed.
Nth exposure.

Covid gets around, or through the mask.

Children can't control their environment in the same way adults can.

They've been keeping this up every day, for years.

We can't contain it at home and everyone gets sick. Cheese being hit by a laser beam.
The problem with schools and hospitals is that COVID policy is as silly as firing laser beams at cheese repeatedly.

There is no attempt to control infection.

In fact, the opposite is true. Infection is encouraged. Updated Swiss Cheese Model graphic
No single layer of cheese can cope with so many laser beams.

Obviously we need more cheese.

We should use all the cheeses.

But critically, we need fewer laser beams. Updated Swiss Cheese Accident Model.
The Swiss Cheese Model presumes that we are TRYING to prevent accidents (or COVID).

We are not.

It's all lasers and no cheese.
If there are fewer laser beams, it's possible for a single layer of cheese to keep you safe for a long, long time.

Maybe even for years.

We need to reduce the frequency with which children are exposed to Covid.

Stop firing so many laser beams at cheese. Image

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More from @Ninawildflower

May 13
I'm going to weigh in on this extremely cautiously.

Because my academic training and personal inclination is not to jump to conclusions.

I'm not a primary teacher. I teach secondary. I have questions instead.🧵
Of course this could be an effect of repeated COVID infections.

There's a wealth of evidence showing COVID can impact the brain. Is this further evidence of this impact, from professionals who know the child really well and can pass judgement?

Or are there other factors?
It's unlikely to be COVID vaccines. Primary age children are unlikely to have received them.

My first question:

How many primary teachers have been teaching long enough to pass judgement?

Many of my colleagues have taught the lion's share of their careers in the pandemic.
Read 6 tweets
Apr 18
The exception that proves the rule.

I was told recently:

“I don't know anyone else who is doing what you are doing. Nobody I know knows anyone else who is doing what you are doing.”

It's possible to change the rules.🧵 Man wearing black respirator mask.
I'm not the first person in the world to be told:

“I don't know anyone else who is doing what you are. Nobody I know knows anyone who is doing what you are.”

I'm a latecomer to this experience, and I'm grateful to those who've done this before.
What does “the exception that proves the rule” mean?

It's contested, but I like this version:

“The exception that proves the existence of a rule that we weren't previously conscious of. The exception draws attention to the rule. Now we can decide if the rule needs changing.” Man wearing FFP3 mask in front of a shelf of board games.
Read 19 tweets
Apr 13
I teach.

But if I'm honest, I don't really like to learn.

That makes me quite unusual.🧵 Man wearing black respirator mask.
Not in the education community. Teachers don't, as a general rule, like learning new things.

If they did, you would see more teachers wearing masks.

It makes me quite unusual in the COVID conscious community.

CC people LOVE learning new things.
We can identify personality characteristics that make someone more likely to be COVID conscious:

- Self discipline & sense of duty
- Nuanced approach to assessing risk

Unfortunately we can't make people better at these things, and end the pandemic through personal choice.
Read 14 tweets
Apr 1
Since you genuinely want to know why I'm still wearing face masks, this is my children's bookshelf.

One of them, anyway.

They have an extraordinary ability to focus and read books.

I want them to maintain this ability for when they go to College.🧵 Man wearing FFP3 mask in front of a bookcase.
There's two parts to this answer.

One is to do with “survivorship bias”.

The other is to do with the effects of COVID on cognition and the brain. Survivorship bias plane diagram.
If you are asking “why are people still wearing masks in 2025?”, you should be asking a different question:

“Why have most people stopped?”

I'm still wearing a mask in 2025 because the reasons most people stopped didn't happen for me. Survivorship bias explanation and diagram from thedecisionlab.com
Read 11 tweets
Mar 17
As we approach the 20th March, I want to talk about something that doesn't happen in UK schools, but maybe it should.

It's called “retrieval practise”. Man with visible mask lines on his face.
When I started teaching, we wouldn't review what had been taught last lesson, a week ago, a month ago, or the previous year.

We had “topic tests”, but once those were done, it could be the end of the year, or the next year, when children encountered those ideas again. Man with visible mask lines on his face.
The problem is, that's not how memory works.

If we don't repeatedly revisit ideas, then we forget them.

This isn't a complex idea. You don't need a lot of training in psychology or neuroscience to understand it. Man with visible mask lines on his face.
Read 20 tweets
Dec 16, 2024
I'm a teacher, so I take work home with me.

These lines - no. They soon fade.

But with 1 week to go, I don't want to bring home #ChristmasFever

Usually I write about how easy it is to wear a mask. But this🧵is about how hard it is, and how to understand why others don't mask. Man with visible mask lines on his face.
I try to raise awareness of COVID in schools. It never went away.

But this week, there are lots of other diseases around that can spoil our holidays. It's not all COVID.

Let's imagine a teacher decided, this weekend, that they didn't want to get #ChristmasFever this year.
Schools weren't made Covid-safe in 2024. Maybe next year it will happen.

I've been doing this since 2021. There are lots of reasons why I've been able to sustain masking.

Would it be easy for someone to START doing this right now? Man wearing respirator mask and holding guitar.
Read 17 tweets

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