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Monday, 21 December 2020

Day 280 of self-isolation - Virus version two

Virus version two

Those of us who are familiar with computer viruses, are very familiar with the concept of variants. Jerusalem virus started life as a single virus; eventually there were dozens of distinct variants (some variants had very minor differences, some substantial).

The original Jerusalem had a big problem. It would infect COM files and EXE files. It tested COM files to see if they were already infected, and left them alone iif they were. But you can see from the code that the author intended the same for EXE files, changed his mind about how to do it, and got it wrong. As a result, EXE files would be infected again and again, growing longer and longer, until the load time became so noticeable that the problem would be investigated.

Some subsequent versions, didn't have that problem, and as a result, were better at surviving and, therefore, better at spreading.

The same happens with biological viruses, although the mechanism isn't people rewriting viruses, it's evolution by natural selection. If a faster-spreading virus results because of a mutation, then that faster spreading virus will prevail over the slower one. The mutation is N501Y, and it affects the spike of the virus, the way it gets into our cells. The variant is called VUI-202012/01. VUI means "Variant Under Investigation", so it's full name would be SARS-Cov-2;VUI-202012/01.

Apparently, the new variant (I'll call it Covid-19.b, using computer virus nomenclature as agreed by Caro in 1989) spreads 70% faster than the old one. I'm not sure what that means. The R number of Covid-19 was about 3, so does that mean that the R number is 5? The R number in London is 1 to 1.2 (lower because  of the restrictions). So does that mean that Covid-19.b is 1.7 to 2? This is very bad news. The number of new infections yesterday was 35928, and that's more in one day than ever before. For comparison - the daily number last April was around 5000. This is very, very bad news.

Apparently, 60% of new infections are Covid-19.b. That is also very bad news, and it's the reason why people are thinking that  Covid-19.b is more infectious . But it's thought that the vaccine will still work (we aren't certain - it hasn't been tested). But if the vaccine targets the "protein spike" and the spike is sufficiently the same, then the vaccine will work on Covid-19.b, just as most computer variants of Jerusalem were detected by the test for the original Jerusalem.

Naturally, everyone is concerned about this. In particular, an increasing number of countries are banning travel from the UK, to try to avoid incoming Covid-19.b.  Italy, Ireland, Belgium and the Netherlands are some of them, but this is a fast-changing scenario; that won't be the final list.

Up till now, there hasn't been much evolutionary pressure on the virus, so it's evolved a lot more slowly than, for example, influenza. But that will change. When the vaccine is in widespread use, the pressure on the virus will be to evolve a version that is vaccine-resistant.

And so it goes.




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