Social distancing

– how it works

There's a lot of talk about social distancing right now. We need to cut down our physical interactions with other people and keep a distance from each other to slow down the rate of the spread of the corona virus.

In this article, we go through a number of simulations to examine how a spread of an imaginary infection could be affected by social distancing.

How big is a social circle?

We start off by looking at how many people might be part of a social circle. Since there are no real people in our simulation, we will instead talk about dots. A dot is like a human being, but simpler.

This is Dot

We'll see how many others dots it comes in direct or indirect contact with, and we'll also see how that changes if we let the dot exercise social distancing.

This is Dot's family

We decide that Dot has two children and a partner, in this network there are now four dots.

Some friends and coworkers

In addition to the family, Dot meets a couple of colleagues and friends every day. There are now 10 dots in the network.

Dot's friends and families and their friends and family.

Dot's friends and family have their own families and friends – together the network is made up of 60 dots.

Some dots have more contacts than others, for example, there is a coworker here who every day meets 10 other dots, maybe it works in sales?

And those dots also meet other dots...

Now it's suddenly 360 dots – that is, 300 more than in the last picture.

...and those dots will in turn interact with even more dots...

And now they are 2160. This could continue until all the dots are connected.. But we won't, we will stay here, four steps from Dot.

Three steps from Dot

Let's go back one level and look the network again. There are 360 dots at this level.

Now let's see what happens if they practice some social distancing – and reduce the number of other dots they interact with.

Dot works from home?

Now three of Dot's coworkers disappeared from the network and thus the friends of the colleagues also disappear from Dot's indirect network. A total of 165 dots disappeared.

Dot opts out of some social visits

Now two of Dot's friends disappeared from the network and thus also their contacts.

What if all the other dots do the same?

This is what happens if the dots who are left also practice social distancing and limit their contacts to about four dots each.

Social distancing, four steps from Dot

Let's zoom out again. If all dots in the large network practice social distancing we are left with 213 dots compared to the 2160 dots we looked at earlier. The bottom line is that if Dot and it's friends distance themselves in the same way, there will be 213 left – instead of 2160 dots. We will look one last time at how many dots there would have been without social distance – scroll down a little more.

No social distanceing

Do you see the difference? It might just work!

How the speed of the spread is affected by distance

Now we will test a couple of simulations where a dot virus spreads between dots. We'll see how fast it's possible to spread a fictitious virus if the dots are close or far apart.

It works like this: We start off with a single infected Dot. Around this dot there is a large circle and all dots inside this circle have an 65% change of becoming infected. The infected dot becomes immune. We then repeat the cycle until there are no longer any infected dots.

As we saw in the dot visualization earlier, the distance between dots depends how many dots you actually meet and not just how far away you keep from each other. For our simulation now we will try to imagine that the dots who are close to each other physically, also are close to each other socially.

Remember they are simulations, which means that the results can be different each time, so try pressing the purple buttons several times.

And one last thing, these simulations only apply to our dots, and when they are scattered over a flat surface like we see below. When trying to predict the spread of a disease in real society, and with people instead of dots, you take into account other things such as where they live, that social contacts often take place in clusters and other complicating factors.

The dots are close together

Did you push the button? Do you see that the curve goes steeply up and down? That's what it looks like when the spread goes fast.

Let's see what it looks like when they're farther apart. It's the same number of dots as in the simulation above, but more spread out so they look smaller.

The dots are spread out

Do you see that the simulation took longer to finish? The curve of how many dots were simultaneously infected was also more flattened, there were fewer who got the dot-virus at the same time.

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Oskar Nyqvist

SVT Datajournalistik

Publicerad: 31 march 2020