1/ Some people are looking at this map and saying: "it must have come from Europe". Here are a few reasons why that is unlikely.

2/ Though B.1.1.7 was especially prominent in Kent, the 2nd sequence ever sequenced was found in London, a day after the 1st. Due to superspreading it isn't possible to pinpoint for sure whether it originated in Kent or London. (If London, there's no argument for the continent).
3/ And suppose we did believe the new variant was introduced from abroad. Would we expect it to be introduced by sea or air? Far more arrivals to the UK in August/September occurred by air compared to sea.
4/ Genetic evidence. Suppose this highly transmissible variant had arisen in some other country, and made its way through France to the UK. It would also have left lots of descendants in Europe. We can look at a genetic tree of sequences and see that that is not the case.
5/ The grey/orange sequences here are UK sequences and the others are from an array of other countries. Specifically I've highlighted a lineage in Denmark which represents spread from a single introduction to Denmark, ultimately from the UK.
6/ Given there is evidence of spread from a single point in the UK, if the UK was not the source of the outbreak we'd expect all these UK grey sequences to group together, like these Danish sequences do.
7/ We'd expect to see at least some European "outgroups", looking like more distant relations on the family tree. But we don't.
8/ You can explore the tree more at https://t.co/XpB0fPkgo1
9/ One doesn't even necessarily need to invoke these phylogenetic arguments. We've seen how quickly this strain has taken over in the UK. We know it has not yet taken over in France. If it had existed in France before the UK, it would be the dominant strain there already.

More from Society

I've seen many news articles cite that "the UK variant could be the dominant strain by March". This is emphasized by @CDCDirector.

While this will likely to be the case, this should not be an automatic cause for concern. Cases could still remain contained.

Here's how: 🧵

One of @CDCgov's own models has tracked the true decline in cases quite accurately thus far.

Their projection shows that the B.1.1.7 variant will become the dominant variant in March. But interestingly... there's no fourth wave. Cases simply level out:

https://t.co/tDce0MwO61


Just because a variant becomes the dominant strain does not automatically mean we will see a repeat of Fall 2020.

Let's look at UK and South Africa, where cases have been falling for the past month, in unison with the US (albeit with tougher restrictions):


Furthermore, the claim that the "variant is doubling every 10 days" is false. It's the *proportion of the variant* that is doubling every 10 days.

If overall prevalence drops during the studied time period, the true doubling time of the variant is actually much longer 10 days.

Simple example:

Day 0: 10 variant / 100 cases -> 10% variant
Day 10: 15 variant / 75 cases -> 20% variant
Day 20: 20 variant / 50 cases -> 40% variant

1) Proportion of variant doubles every 10 days
2) Doubling time of variant is actually 20 days
3) Total cases still drop by 50%

You May Also Like

I think a plausible explanation is that whatever Corbyn says or does, his critics will denounce - no matter how much hypocrisy it necessitates.


Corbyn opposes the exploitation of foreign sweatshop-workers - Labour MPs complain he's like Nigel

He speaks up in defence of migrants - Labour MPs whinge that he's not listening to the public's very real concerns about immigration:

He's wrong to prioritise Labour Party members over the public:

He's wrong to prioritise the public over Labour Party