Random Rants, Raves and Ramblings

Covid Policy in 500 Words

The R number says how many new people get infected, on average, by one infected person. An R of 2 means the first case infects two people, those two go on to infect four and so on.

The R number is made up of two components. One is how easily the virus is transmitted. The other is how many people we meet, and how careful we are to avoid transmission.

The first component is only determined by the nature of the virus. The new variants are more easily transmitted, so under the same conditions the new variants have a higher R number.

The second component is only determined by our behaviour. The more careful we are, the lower the R number. Face masks, social distancing and vaccines all help push R down.

Crucially, the R number is not dependent on how many infections there are. If the virus is the same and people’s behaviour is the same, 100 cases become 200 cases in the same time that 1000 cases become 2000 cases.

It is tempting to set the rules on an ad hoc basis depending on infection numbers: slacken the rules (let R grow above 1) when few people are infected and tighten them when a certain panic level is reached. But now you see that even if you set the “pain threshold” very high, that will not result in more relaxed rules on average.

This explains why countries whose governments were loath to set restrictions (e.g., the UK) end up being locked down just as often as countries where the government was more careful (e.g., Denmark). The only difference is how many people are sick and dying.

But what about countries like New Zealand and Taiwan? They’re virtually Covid free! Well, that’s the twist in the tale. The trick is to smack down on the infection (keep R well below 1 long enough) until so few people are infected that you can handle them individually. Then it’s enough to shut down a village rather than the whole country. A single case in New Zealand is news.

Remember that the R number doesn’t depend on the number of cases. The R number for Covid-19 in New Zealand is very large – there are almost no restrictions in place. It’s just that zero times a large number is still zero.

By contrast, countries that try to “manage” a large number of infections are simply giving the virus time and space to evolve. When more people are sick, more virus particles are replicating and mutating. It is no wonder that countries like the UK have proven the perfect breeding ground for new variants that require ever stricter measures, and new vaccines, to combat.

This way, Covid-19 and its offspring will be with us for generations. Meanwhile, we can always choose to get rid of it completely. All it takes is the political courage to keep restrictions in place until there are no known cases left, and then to remain watchful for new cases.


I was chatting with my Danish twin brother who is quite active in the whole Covid statistics thing. I mentioned to him that various governments simply seem to have a mental "ideal infection rate" and that the totality of their policy is to try regulating the system towards that target. And since they all respond forcefully but late, the system oscillates. Yes, he replied, but the silly thing is that the growth is exponential, so all they're doing is regulating R to 1 while the actual infection rate doesn't figure. And, he continued, you sound somewhat surprised so we have to assume that few people will grasp this intuitively. Touché. So I took it as a challenge to turn that observation into something that non-mathematicians can follow.

Sunday 07 March 2021