The number of cases in the UK of the Indian COVID variant, also known as the Delta variant, has risen by more than 5,000 since last week.
They have gone up by 5,472 to 13,760, according to Public Health England (PHE).
Experts from PHE now believe that Delta has overtaken Alpha (also known as the Kent strain) as the dominant coronavirus variant in the UK.
The most affected areas remain Bolton, where cases have risen by 795 to 2,149, and Blackburn with Darwen which has seen 368 new cases, bringing it to 724 in total.
There are encouraging signs that the transmission rate in Bolton has begun to fall and that the actions taken by residents and local authority teams have been successful in reducing spread, according to PHE.
Dr Jenny Harries, chief executive of the UK Health Security Agency, said: “With this variant now dominant across the UK, it remains vital that we all continue to exercise as much caution as possible. The way to tackle variants is to tackle the transmission of COVID-19 as a whole. Work from home where you can, and practice ‘hands, face, space, fresh air’ at all times.
“If you are eligible and have not already done so, please come forward to be vaccinated and make sure you get your second jab. It will save lives.”
“In Bolton, local teams have gone door to door in targeted areas on consecutive weekends to distribute test kits, share vital safety messages and encourage people to get the vaccine at a local drop-in centre. Take up of both testing and the vaccine has been positive.
“Blackburn with Darwen has also seen local teams making door-to-door visits, and over 10,000 additional PCR tests have been given out. Mobile testing units have been deployed to the area and wastewater sampling continues, in order to track the spread of the variant.”
PHE also said outbreaks and clusters in primary and secondary schools are at low levels but there has been a slight increase over recent weeks, in line with higher levels of the Delta variant circulating in the community.
The latest PHE data suggest there have been 97 confirmed COVID-19 outbreaks in primary and secondary schools that have had at least one variant case linked to them over the most recent four-week period. This represents around one in 250 schools.