Lockdown latest: When restrictions could be eased in UK
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The number of new cases is being tracked through hospital admissions, a new testing study in the community and data that will be gathered from people coming forward for tests.
Mr Hancock suggested there is no prospect of easing the lockdown yet, and that coronavirus cases need to drop substantially before the next phase of isolating infected people and their contacts can be truly effective.
Through a process of mass testing and by isolating infected people and their contacts, ministers hope that future localised outbreaks of coronavirus can be kept under control.
Mr Hancock told Radio 4's Today programme: “Now that we're at the peak, and we very much hope that things will start to slow down and, if and when they do, then the speed with which the number of new cases reduces will frankly will determine how long we need to keep the measures on and that is as yet unknown.”
He said it was not quite the case that mass testing and contact tracing needed to be in place before the current restrictions are eased, but said contact tracing worked better when the number of infections was pushed right down.
“The truth is that we need to get the number of new cases down, right down, and the lower you go, the more effective contact tracing is because the more resources you can put into each individual case that gets a positive test.
“You can really make sure you can get hold of all of their contacts and get them, in many cases, to self-isolate.
“The smaller the number of new cases, the more effective the test, track and trace system will be.”
The government has expanded its Covid-19 testing programme to all key workers and their households if they have symptoms as it tries to hit its 100,000 tests a day target by Thursday next week.