A huge door-to-door testing mission is getting under way in a bid to find "every single case" of a new coronavirus variant in England.
On-the-spot doorstep tests, home testing kits and mobile testing units will be used to try to reach 80,000 people in eight specific areas.
The efforts are to track down and stop the spread of the more infectious South African variant of the virus.
What is the South African variant?
A variant is a different version of a virus - all viruses change and mutate so this is not unusual.
So far thousands of new variants have been found across the world, but health experts are currently focused on versions found in the UK, South Africa and Brazil.
Scientists are studying these mutated versions to understand what makes them different, and whether those differences may make them better at spreading between people, for example, or if it means changes need to be made to the vaccines that have been developed.
In most of the areas, home testing kits are being delivered and collected, while some are also providing mobile testing sites.
In Kent, police, council workers, fire-fighters and other agencies will visit homes to carry out on-the-spot tests of everyone in the household.
Mr Hancock also said it was "absolutely vital" that people in these areas where cases of the variant had been identified minimise all social contact.
Which areas are affected?
The list of areas being tested
Parts of the ME15 postcode area in Kent,
Parts of the WS2 postcode area in Walsall in the West Midlands
Parts of the GU21 postcode area in Woking, Surrey
The CR4 postcode area around Pollards Hill in south London
Tottenham Hale in the N17 area of north London
The W7 area in Hanwell and West Ealing, London
The EN10 postcode area in Broxbourne
Parts of the PR9 area in Southport