The Delta variant of COVID-19, or the B1.617.2 highly transmissible variant of concern (VOC) first identified in India, has now become the dominant VOC in the UK as infections rose by 5,472 in a week to hit a total of 12,431, health officials in Britain said on Thursday.
Public Health England (PHE), which monitors all COVID variants in the country, said that experts now believe that Delta has now overtaken Alpha the VOC first detected in the Kent region of England.
PHE also said that early evidence suggests there may be an increased risk of hospitalisation with Delta compared to Alpha, although more data is needed to have a more definitive view on that.
With this variant now dominant across the UK, it remains vital that we all continue to exercise as much caution as possible, said Dr Jenny Harries, Chief Executive, UK Health Security Agency.
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, she said. According to the breakdown of official figures, this week 278 people with the Delta variant attended hospital in an emergency.
Last week, 201 people attended hospital.
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Once again, the majority of these had not been vaccinated, PHE said.
The areas most affected by the Delta variant remain in the north west of England with Bolton, where cases have risen by 795 to 2149, and Blackburn with Darwen which has seen 368 new cases, bringing it to 724 in total.
PHE said 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.
Experts continue to urge people to remain cautious as the country approaches the next stage of the roadmap, with June 21 scheduled as a date for an end of all lockdown restrictions.
Variant cases are on the increase in several areas and it is absolutely crucial that everyone plays their part in preventing their spread, PHE said.
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 was described as "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 said its health protection teams continue to work with local authorities and schools to carry out surveillance of COVID-19 cases in schools to understand and reduce transmission in these settings.