Residents in a west London borough are being asked to take a rapid Covid test after a number of new cases of the South African variant were identified.
Earlier this month, one of Ealing's residents tested positive for the strain, despite never having travelled to the country.
A "small number" of cases of the variant have since been detected in Acton, Greenford, Southall and West Ealing.
Ealing Council, which has already carried out surge testing in parts of the borough, is now asking residents across the entire borough to have a rapid test.
Residents are encouraged to visit local community test sites from Thursday.
It comes after studies suggested that current vaccines offer less protection against the South African variant, which has a key mutation – E484K – that is thought to help the virus evade parts of the immune system.
The mutation has been worrying scientists and is also found in the Brazil variant of the virus as well as some cases of the variant originally identified in Kent.
Meanwhile, Moderna has produced a vaccine that works specifically against the South African variant of coronavirus, with trials due to start in the US.
The firm is experimenting with several potential methods of combating new variants of coronavirus, with a view to potentially offering new or booster shots.
Moderna is looking at whether an additional booster shot targeting the South African variant could be given to people, and is working on a combined jab that mixes its current vaccine with the new one.
The UK has ordered 17 million doses of Moderna’s original vaccine, with delivery expected from the spring.
