A massive system to find people who come into close contact with those infected with coronavirus will start in England on Thursday, Boris Johnson has said.
The prime minister said it “will change people’s lives”.
The aim of the test and trace system is to move from lockdown for all towards more targeted measures.
However, scientists have warned it is not a “magic bullet” and may prevent between 5% and 15% of infections.
Northern Ireland has its own version up and running, Scotland has announced its own system will start on Thursday and Wales’ system is due to start in early June.
As is currently the case, anyone who develops symptoms of coronavirus – a persistent cough, fever or a sudden loss of taste or sense of smell – will have to isolate for seven days and the rest of their household for 14 days.
The difference is that from Thursday, everyone with symptoms should ask for a test online or call 119.
If the test comes back negative, everyone in your household can go back to normal.
But if the test comes back positive, the NHS Test and Trace team will get in touch – via text, email or phone call – to discuss who you have come into close contact with.