Thread by @mattuthompson

So. Advised by a friend who is an epidemiologist, allow me to try and explain as best I can what’s going on.

Here followeth a quick THREAD

#coronavirus

Any infectious disease has a basic reproduction number: the number of people that one infected person will go on to infect, absent any immunity (known as R0)

Let’s say that number is 3. So if I have the disease, I’ll infect 3 other people on average.

(2/?)

But if 2 out of 3 of those people become immune, I can’t infect them. So where once I’d have infected 3 people, now I only infect 1. The epidemic can’t grow.

And if you can get R0 below 1,so each infected person infects *less* than one person, the disease eventually fizzles out

Take measles as an example. We started to get measles outbreaks because idiotic anti-vaxxers tipped the balance so that R0 rose above 1 and each infected person started infecting more people.

(4/?)

Now you can get to the magic tipping point by creating herd immunity, either through vaccinating or letting people catch the disease.

Or you can do it another way.

(5/?)

You can take preventative measures (social distancing, hand washing) so I as the carrier simply don’t infect 2 of the 3 people I’d otherwise have infected.

This is maybe better thought of as herd protection, rather than immunity.

(6/?)

The trouble with the herd protection, rather than immunity, is that it only lasts as long as the controls are in place. Once they’re lifted, you’re vulnerable to another epidemic.

Longer term, therefore, achieving immunity is arguably a better solution.

(7/?)

That, at least, is a purely mathematical argument.

It doesn’t make value judgements about whether we should accept that some people will die. But there it is.

(ENDS)