Coronavirus updates as they happened: Test and trace system revealed as UK PM faces MPs - BBC News
A test and trace system to try to curb infections is to begin in England on Thursday.
Has the US conducted the most Covid-19 tests?

US President Donald Trump has tweeted that the country has tested 15.5 million people for Covid-19, and that the figure is "by far the most in the world". But does this claim stand up to scrutiny? In fact, the BBC Reality Check team has fact-checked the president's claims on testing before, and found them wanting. It is difficult to find truly accurate numbers for global testing because different countries have different ways of conducting and counting tests. This means that in order to compare numbers, we have to decide whether figures from around the world are comparable, or even trustworthy. According to figures from China's state news agency Xinhua, the combined number of people tested in just two areas totals around 17 million – that's 10.41 million in the province of Guangdong and 6.5 million in Wuhan , where the city authorities say they plan to test the entire population of around 11 million. To attain these figures, the Chinese authorities have been "batch testing" - testing multiple samples in groups. They expect the vast majority of Covid-19 tests to be negative, which makes sense statistically, but if samples within a certain batch test positive, the samples are then tested individually. So, the total for the whole of China's estimated 1.4 billion population is likely to be much higher than Mr Trump's 15.5 million. But according to BBC China analyst Kerry Allen, there's no way to independently check how many individual tests have been carried out.