The Delta variant of coronavirus - formerly known as the Indian variant - is now the dominant strain of new cases in Wales, it has been confirmed.
Public Health Wales said there were now 315 confirmed cases of the Delta variant - a rise of 131 since the previous variant update on June 10.
The cases were mainly linked to community transmission, the agency said, with the majority of new Delta cases not being connected to international travel.
Public Health Wales said that the majority of the Delta cases in Wales have been focused around a cluster of cases in the north and a cluster of cases in the south.
But it added that it was beginning to see unlinked cases in these areas and elsewhere in Wales.
Today, 247 new cases of coronavirus have been confirmed in Wales, but no new deaths have been reported.
The Delta variant's rise to becoming the dominant strain in Wales was "predicted" according to the agency.
Dr Giri Shankar, incident director for the coronavirus response at Public Health Wales, said: "This is a significant development, but one we have predicted, as we know the Delta variant is easier to catch than the previously dominant Alpha variant.
"It is thought that increased mixing is contributing to transmission and we are concerned at this rise in cases.
"There is much we can do to protect ourselves and others.
"Latest evidence shows that both Pfizer and AstraZeneca vaccines are effective against the Delta variant after two doses and so it’s so important to take up the offer of both vaccines."
Speaking at Monday's coronavirus press briefing, economy minister Vaughan Gething appeared to indicate that Friday's scheduled move into Coronavirus Alert Level One was not guaranteed with the developments around the Delta variant.
He said: "The First Minister will confirm the move at the end of the week.
"The Delta variant has taken off much more significantly in Scotland and in England. Their case rates are materially higher than here in Wales and we're starting to see the real world impact of whether the Delta variant does cause more people to need hospitalisation - and actually the impact that vaccination has or hasn't had on reducing the numbers of people who will need hospital treatment.
"The big risk is both people coming to harm and potentially losing their lives, and I certainly don't want to go back to where we have been at various points in the last year and more with the terrible numbers of people who have lost their lives.
"But also, even if we don't see significant numbers of people losing their lives we need to think about the impact on hospitalisation.
"So that real world will be really important for us.
"We will have to consider that as we make choices this week and as we then make choices what will come after this next phase of easing.
"There is an element of uncertainty but you only have to wait until Friday for the First Minister to confirm the position here in Wales."
The all-Wales coronavirus infection rate currently stands at 18.4 per 100,000 people with a national test positivity rate of 1.8%.
Meanwhile on Monday, Health Minister Eluned Morgan confirmed that all eligible adults in Wales have now been offered a first dose of a coronavirus vaccine.
The reaching of the milestone was six weeks ahead of schedule, the Welsh Government said.