A new variant of coronavirus which was found to be circulating in England is already present in Wales, the Welsh Government has confirmed.
On Monday, the UK government said the variant “may be associated” with a faster spread in south east England.
The Welsh Government said there are at least 10 confirmed cases in Wales and more are expected to be identified.
More than 1,000 cases have been recorded across 60 English council areas.
Matt Hancock, the UK government minister in charge of the NHS in England, said there was “nothing to suggest” it caused worse disease or that vaccines would no longer work.
Announcing tougher restrictions in London and parts of Essex and Hertfordshire, he said: “We’ve currently identified over 1,000 cases with this variant predominantly in the south of England, although cases have been identified in nearly 60 different local authority areas.
“We do not know the extent to which this is because of the new variant, but no matter its cause we have to take swift and decisive action which unfortunately is absolutely essential to control this deadly disease while the vaccine is rolled out.”
He said the World Health Organization had been notified of the new variant and UK scientists were doing detailed studies.
The Welsh Government said: “It is natural for a virus to mutate over time and we have seen a range of mutations in Wales.
“In relation to this particular mutation, we have identified 10 confirmed cases and five probable cases through sequencing that took place during November. Further sequencing is under way and we expect to identify further cases.
“Public Health Wales is actively looking for this variant and will be tracking any other Welsh cases as they emerge. Our findings will be feeding into the work being undertaken across the UK.”
There is a simple rule for understanding all “new strain” or “new variants”: Ask whether the behaviour of the virus has changed.
This is crucial as viruses mutate all the time, it’s just what they do. And so far we’ve been given the “scare” but not the “answer”.
Matt Hancock said the new variant of coronavirus “may be associated” with the faster spread in the south-east of England.
This is not the same as saying it “is causing” the rise and Mr Hancock did not say this virus has evolved to spread from person-to-person more readily.
New strains can become more common for reasons that have nothing to do with the virus.
One explanation for the emergence of the “Spanish strain” over the summer was tourism.
So at the moment there are scary headlines everywhere, but still no scientific detail to know how significant this is.
The news of the new variant comes as cases continue to rise in Wales.
On Monday it was revealed Wales was already breaching some of the key indicators used to determine if the country goes into lockdown.
First Minister Mark Drakeford said a lockdown could be introduced after Christmas if rates do not begin to fall.
Public Health Wales figures on Monday showed Merthyr Tydfil had the highest case rate in the UK, with 870.3 cases per 100,000 people over the most recent seven days.
Eight Welsh counties were among the 10 areas with the highest case rates in the UK.