Positive cases of Covid-19 are increasing sharply in parts of the UK, with around one in 60 people now testing positive in Wales and one in 85 in England, figures suggest.
Around half of the most recent positive cases in England could be the new variant of Covid-19, with the proportion rising to as high as 68% of cases in London.
The findings are from the latest infection survey from the Office for National Statistics (ONS), which is based on regular samples of positive nose and throat swab results.
They show that an estimated 52,200 people in private households in Wales had Covid-19 between December 12 and 18.
This is the highest estimate for Wales since the survey began in the summer, and is up from 33,400 people for December 6 to 12 – the equivalent of a jump from around one in 90 people testing positive to around one in 60.
The rate has also continued to rise in England, where an estimated 645,800 people in private households had Covid-19 between December 12 and 18, up from 567,300 people on December 6 to 12.
This is the equivalent of a jump from one in 95 to one in 85 people.
The estimates do not include people staying in hospitals, care homes or other institutional settings.
Meanwhile separate figures from the ONS, again just for private households, suggest that around two-thirds of recent positive cases in London, eastern England and south-east England could be the new variant of Covid-19.
In London, 68% of positive cases in December 14 to 18 were estimated to be genetically compatible with the new variant, while in eastern and south-east England the estimate is 65%.
For England as a whole, the ONS estimated 49% of new cases could be the new variant.
The lowest estimates are for north-west England (7%) and the East Midlands (13%).
There is a similar variation in the overall percentage of people testing positive in each of the regions of England.
The rate of infection has "continued to increase sharply" in London, eastern England and south-east England, the ONS said.
London now has the highest rate of people testing positive, with an estimated 2.1% of people in private households testing positive for Covid-19.
This is followed by south-east England (1.4%) and eastern England (1.2%).
The percentage testing positive in south-west England has also increased during the most recent week, while rates have continued to decrease in north-west England and Yorkshire & the Humber.
When modelling the level of infection among different age groups in England, the ONS said rates have increased in all groups except for those aged 50 to 69, where there are early signs of an increase, and for those aged 70 and over where there are early signs of a decrease.
Rates remain highest among secondary school-aged children (school years 7 to 11).
The ONS also published its latest estimates for Northern Ireland and Scotland.
In Northern Ireland, an estimated 10,100 people in private households had Covid-19 between December 12 and 18, or around 0.55% of the population.
This is up from an estimated 8,500 people for the period December 6 to 12, or 0.47% of the population.
But in Scotland, an estimated 37,100 people had Covid-19 between December 12 and 18, or 0.71% of the population – down from 52,500 people, or 1.00%, for December 6 to 12.