We’ve had a while to study the coronavirus but it, too, has had time to study us.
A new mutated strain is spreading rapidly across the south-east of England, prompting fears of an escalation just as vaccine breakthroughs were providing hope.
Experts reassure there is no evidence that this new strain is more deadly.
But it could be up to 70% more infectious, and increase the "R" rate - or how much it spreads - by 0.4.
A faster spread means more cases, and inevitably more deaths.
It was first seen in Britain in September.
By the start of December in London, 62% of cases were due to the new variant.
Much is unknown about the strain but experts are hopeful current vaccines should still be effective.
The vaccines work by targeting different areas of the virus - including that all-important and distinctive shape of the protein spike.
The new variant contains 23 changes to the original.
But many of those relate to how it binds to and enters cells.
Julian Tang is virologist at the University of Leicester.
"So people must have looked at this N501Y mutation and looked at where the mutation has occurred and tried to predict how much that would have changed the protein shape. And it sounds like they figured out that, in fact, it won't change it that much. So the vaccine induced antibodies to the S protein should still bind to it and give you protection from the virus with the existing vaccines.”
Experts warn that future mutations of the coronavirus remain unknown.
Influenza and HIV have continually mutated over the years, evading vaccines.
The key is to slow a virus’s spread before it has a chance to adapt too radically.
“If enough mutations hit that S protein over the next 12 months, for example, just like with flu, you may need to change, tweak the vaccine a bit to fit the new virus. So maybe a year from now, you might see a few more new mutations that may start to affect the vaccine.”
While the new strain has also been detected in Australia, Italy, and the Netherlands, it appears to be most dominant in southern England - prompting numerous countries to close their borders to UK travellers.
It was first discovered through Public Health England’s genomic surveillance.
Britain reportedly possesses some of the best global analysis of mutations.
It’s possible it’s just able to see what is already present in other countries.