A new variant of coronavirus, which has been linked to the faster spread of Covid-19 in the south of England, has been identified in Wales.
The Welsh Government said 10 cases have already been confirmed and they expect more to be identified.
Experts have said it is too early to be worried about a new variant of coronavirus, or make any claims about the potential impacts of the virus mutation.
On Monday, England's Health Secretary Matt Hancock said the new variant may be linked to the faster spread of the virus in the South of England.
He stressed there is no evidence to suggest the variant is more likely to cause serious disease, and that it is highly unlikely the mutation would fail to respond to a Covid-19 vaccine.
The Welsh Government said: "In relation to this particular mutation, we have identified 10 confirmed cases and 5 probable cases through sequencing that took place during November - further sequencing is underway 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."
England's chief medical officer Professor Chris Whitty told the Downing Street press conference there was nothing to suggest a vaccine would not work against the new strain and that current tests can detect it.
He explained: "There's still a quite a small proportion of the population, currently have immunity due to prior infection.
"So there isn't a huge selection pressure on this virus.
"And therefore, it would be surprising - not impossible, but pretty surprising, if this would actually have evolved to be able to get around the virus."
He added that as time goes by selection pressures, when a very high proportion of the population has been vaccinated, mean any new variants that emerge are more likely to be ones which actually are able partially to escape from a vaccine but there's no reason to think that would be happening at the moment.
The emergence of this mutation of coronavirus comes against a backdrop of rising cases in Wales.
Covid rates have risen in 20 of the 22 local authority areas, with Wales' seven-day rate exceeding 450 per 100,000 people.
The biggest rise has been in Merthyr Tydfil, where the rate is up from 470.8 to 822.2 - the highest in Wales.