Parts of Kent and West Yorkshire are the latest areas to be targeted with surge testing after cases of the Indian variant were detected.
Additional testing with genomic sequencing is being rolled out in the CT1 and CT2 postcodes in Canterbury and the ME14 postcode in Maidstone, both Kent.
Surge testing is also being introduced in targeted areas of Bradford, West Yorkshire, health officials said on Friday.
Everyone who lives or works in these areas is being strongly encouraged to take a Covid test - including children aged 12 and over in Canterbury and Maidstone and over-11s in Bradford.
Anyone with a confirmed case of the Indian variant, also known as the 'Delta' variant, is being instructed to self-isolate.
The strain has now overtaken the Kent variant as the dominant strain in the UK, officials confirmed this week.
Scientists are urging Boris Johnson to delay the next stage of his roadmap out of lockdown, set for June 21, due to the ongoing threat posed by the Indian variant.
They fear the strain will spread more rapidly if restrictions ease further later this month.
Downing Street has said there are no immediate plans to stray from the roadmap at this stage.
However worries about new variants, including the so-called 'Nepal' mutation, were cited by ministers as the government reined in international travel this week.
Portugal was axed from the UK's travel green list to the dismay of summer holidaymakers, and seven more countries were added to the red list.
Transport Secretary Grant Shapps said the government was putting 'safety first' and prioritising the next stage of lockdown easing over easing curbs on travel abroad.
Friday brought another rise in daily Covid case numbers, continuing a creeping upwards trend.
The daily Covid case numbers topped 6,000, in the highest levels recorded in three months.
The vaccine rollout, meanwhile, is nearing the 40million first does milestone.
More than three-quarters of the UK adult population has received at least one dose.
Despite case numbers rising, deaths and hospitalisation figures have remained relatively low.
Eleven more deaths were reported nationwide on Friday, following a milestone zero death toll on Tuesday following the Bank Holiday weekend.
England's Covid R rate rose to between 1 and 1.2 on Friday and the epidemic could be growing by as much as 3% each day, official figures showed.
An R number between 1 and 1.2 means that, on average, every 10 people infected will infect between 10 to 12 other people.
Independent Sage scientists urged the Government to "pause" plans to ease England's coronavirus lockdown and issued seven demands amid a "rapid increase" in cases of the Indian variant.
The panel warned that the latest data shows the variant carries increased infectivity and is spreading widely across the UK.
Evidence suggests it may lead to an increased risk of being admitted to hospital compared with the Kent variant, which began ripping through the UK over the winter.
A new study suggests the Pfizer-BioNTech vaccine is less effective at preventing infections with the variant.
