It is not too late for Europe to contain the new variant of Covid-19 exploding in southeast England, a top coronavirus mutation tracker told AFP.
However, there is a fair chance that the strain is already circulating under the radar in other countries, said Emma Hodcroft.
The US-British molecular epidemiologist, based at the University of Bern, is a co-developer on the Nextstrain project, analysing SARS-CoV-2 sequences from around the world to monitor variations that emerge.
The expert has been tracking the current British and South African mutations.
Is it too late to contain the new mutation?
Hodcroft: "On a European level, I don't think so.
"There's a fair chance that there are more cases of this variant across Europe that we just haven't detected yet.
"Low levels of this variant might still be containable. If it's in a few people and those people are doing a good job, following the guidelines, wearing a mask, then it might not spread further.
"So it is worth trying to keep the number of people with this variant down, because that does help us to contain it through other measures.
"If this variant has increased transmissibility, as scientists in Britain seem to really think it does, the best way to counter that is, unfortunately, with the same measures that we take now."
Can it be contained in Britain?
"Within the UK it's tougher because it's much harder to draw the lines.
"Belgium can say things like 'No British flights can land here'. In Britain, it's not really possible to say, 'everyone in London, we're closing the roads, you cannot leave'.
"I'm not saying that it's not still worth trying, but it is going to be hard to keep it contained just in southeast England, particularly with Christmas around the corner."
Should travel from Britain be stopped?
"Countries should be making careful considerations and really thinking hard over the next few days about what measures, if any, they want to impose on British travel.
"I would hope everyone's thinking about it, whatever decision they come to."
How does travel impact on spreading variants?
"Unfortunately, from what we know about, for example, the Spanish variant spreading through the European summer, we know that travel and holiday activities can really transmit the virus or variants of the virus incredibly effectively.
"It becomes a question of how long do you wait... trying to keep that balance of not acting to early but knowing that if you wait too late, you might have missed the chance to contain the spread."
Did the mutation start in Britain?
"The UK is the world leader in sequencing. So if there's a variant and it gets to the UK, it has a good chance of being detected there.
"By chance, if you were pulling sequences from Europe out of a hat, with the most probability you'd pick a UK sequence.
"Even though we may not be able to say for sure that it started in the UK, it does look like it expanded there."
How does stopping the virus spreading affect mutation?
"We can never stop the virus mutating. But we can put the odds in our favour when we keep those case numbers down.
"The less virus there is circulating, the less chance it has of getting into different people with different immune systems, with different vaccination history.
"And so we reduce the chance that it ends up somewhere where it's able to get some mutations that maybe are bad news for humans."
What can sequencing tell us?
"The most reliable way to detect the presence of this variant is through sequencing.
"It's through sequencing that we can see something start to behave differently.
"The main thing is tracking these different variants and trying to identify are any of these variants indicative of something worrying, like increased transmission or resistance to a vaccine or worse clinical outcomes?
"This is almost certainly not going to be the last variant that we're interesting in knowing where it is and how it's travelling."