Residents in a part of Surrey are to be urgently tested for Covid-19 after it emerged the South African strain of the virus may have started spreading in the community.
Two positive cases of the strain – which has been worrying scientists – have been identified in people with no links to travel or previous contact with those affected.
So far, 105 cases of the strain have been identified to date across the UK, but this is the first sign of wider community spread.
Some of the vaccines in use and currently going through approval have shown some effectiveness against the variant.
Surrey County Council said the Surrey Local Resilience Forum is working with Public Health England (PHE) and the Department of Health to carry out a localised "surge testing" programme in the Goldsworth Park and St Johns areas of Woking.
Residents within the affected areas will be asked to carry out a test even if they have no symptoms.
The council said in a statement: "This will enable us, working closely with PHE, NHS Test & Trace and the Joint Biosecurity Centre to closely monitor any community spread of the new variant, and restrict further transmission."
A similar surveillance exercise is expected to extend into an area of Egham in the county.
There is currently no evidence that the variant causes more severe illness.
Ruth Hutchinson, director of public health for Surrey, said: "This is a precautionary measure – the more cases of the variant we find, the better chance we have at stopping it from spreading further.
"By playing your part and taking the test, you'll be helping to keep your community and your loved ones safe.
"It's really important to say that there is currently no evidence that this variant causes more severe illness, so you don't need to worry."
Dr Alison Barnett, regional director at Public Health England South East, said: "The UK has one of the best genomic systems in the world which has allowed us to detect the variant originating in South Africa here in Surrey.
"I urge everyone offered a test to take it up to help us to monitor the virus in our communities and to help suppress and control the spread of this variant."
It comes as Boris Johnson played down fears about vaccines being ineffective against different variants.
During a visit to the Al Hikmah vaccination centre in Batley, West Yorkshire, the Prime Minister told reporters: "We are confident that all the vaccines that we are using provide a high degree of immunity and protection against all variants."
He said the vaccines could be adapted to deal with new variants if necessary.
"The fact is we are going to be living with Covid for a while to come in one way or another," he added.
"I don't think it will be as bad as the last 12 months – or anything like – of course, but it's very, very important that our vaccines continue to develop and to adapt, and they will."
Mr Johnson said there were signs the lockdown measures were working but it was too early to "take your foot off the throat of the beast" by easing restrictions.
"We are starting to see some signs of a flattening and maybe even a falling off of infection rates and hospitalisations," he said.
"But don't forget that they are still at a very high level by comparison with most points in the last 12 months, a really very high level.
"So the risk is if you take your foot off the throat of the beast, as it were, and you allow things to get out of control again then you could, alas, see the disease spreading again fast before we have got enough vaccines into people's arms. That's the risk."