Frontline hospital staff in England are starting to be tested to see whether they have coronavirus.
Workers with symptoms and those who live with people who have symptoms will be checked – starting with hundreds of critical care doctors and nurses.
Tests for A&E staff, paramedics and GPs are expected to follow, and later social care staff will be tested.
It comes as the number of people who have died with the virus in the UK rose by 260 to 1,019 on Saturday.
Latest government fingers show there are now 17,089 confirmed cases in the UK.
In Wales, Scotland and Northern Ireland, health workers are already being tested.
Until now, only patients in English hospitals with flu-like symptoms were being routinely tested but this had led to concerns that without testing, many health and care workers would not know whether they were safe to return to work.
Meanwhile, Scottish Secretary Alister Jack is the latest politician to announce he is self-isolating after showing mild symptoms.
Prime Minister Boris Johnson, Health Secretary Matt Hancock and England’s chief medical officer, Prof Chris Whitty are all self-isolating after testing positive for the virus.
Mr Jack spoke in the Commons on Wednesday, sitting near to the PM and Mr Hancock, although they appeared to follow social distancing rules with spaces between them on the benches.