Video report by ITV Wales Reporter Dean Thomas-Welch
The first case of a new variant of coronavirus known as Omicron has been confirmed in Wales.
The Welsh Government said the case is in the Cardiff and Vale University Health Board area and is linked to international travel.
In a statement, a Welsh Government spokesperson said: "We are prepared to respond rapidly to emerging variants of concern, and intensive investigations and robust public health action are being taken to slow any spread.
"The health impact of the Omicron variant is still being assessed. Currently there is no substantial evidence to suggest the Omicron variant will lead to a more severe form of illness but the data is being kept under constant review.
"As we better understand this variant we will be able to determine the next steps. In the meantime, sticking to the rules, following the steps which keep us safe and taking up the offer of a vaccine continue to be the best way to protect ourselves and the NHS."
Cases of the new variant have also been confirmed in England and Scotland, as well as Europe and across the globe, including Australia, Canada, Israel and Japan.
There have been moves to tighten restrictions on international travel and to expand the UK's vaccine programme to slow the spread of the new variant for as long as possible.
Wales' health minister Eluned Morgan spoke about the new variant during a press conference, just three days before it reached Wales.
Speaking on Tuesday, Ms Morgan told journalists it was "simply a question of time" before the variant arrived in Wales.
But she said it was "too early to say" if Wales would see a return to very heavy restrictions, including a lockdown or 'fire-break', amid concerns over the virus.
"This is clearly a very worrying time for us all," she added.
"We had hoped by now to be able to think about a future not overshadowed by the pandemic. But we now face the uncertainty about a new variant of coronavirus just before Christmas.
"There is still a lot we don’t know about this variant. We won’t know the answers until more research has been done.
"There's never been a more important time to work together to protect our families and loved ones.
"It's too early to say yet what the situation is likely to be as we enter the Christmas period, but I would urge people to act with caution over the Christmas period. And to take seriously the situation, and the threat, of mixing with other people indoors during this time."
'It is simply a question of time before Omicron arrives in Wales': Eluned Morgan speaking on Tuesday
In response to the first case of Omicron, Dr Meng Khaw, National Director for Health Protection and Screening Services for Public Health Wales, said: “The number of mutations in the Omicron variant is concerning, but new variants are anticipated.
"We keep variants under constant review, and we work with UK partners to identify, detect and monitor new and known variants. The Delta variant continues to be the dominant strain in Wales.
“The single best thing you can do to protect yourself, your community and the NHS against new variants of coronavirus is to take up the offer of a vaccine.
“You can also protect yourself and others by maintaining a social distance where possible, washing hands regularly, keeping homes well-ventilated, and working from home if you can. Use a Covid Pass and a face covering where required.”
Scientists continue to study the possible threat posed by Omicron.
A study in South Africa, where the mutation was first detected, has suggested that the variant has "substantial" ability to cause reinfection in people who have previously had Covid.
The research, which has not been peer-reviewed, found people who had tested positive for coronavirus could pick up the virus again, potentially causing a wave of infections in those with some prior immunity.
It did not say how the variant will behave when spreading in a highly vaccinated population such as the UK, or whether the virus can evade the protection offered by vaccines against severe disease.
But experts in the UK believe their research on the impact of booster vaccines could offer hope in the fight against Omicron.
The CovBoost study found that booster jabs may well offer good protection in the face of the variant.