Scottish Secretary Alister Jack is self-isolating after developing mild symptoms of coronavirus.
The Conservative MP for Dumfries and Galloway said he has a mild temperature and a cough.
He has not been tested for Covid-19 but is self-isolating and working from home.
Mr Jack said: “In the past 24 hours, I have developed mild symptoms associated with coronavirus.
“In line with medical guidance, I am self-isolating and working from home.”
The MP has been at home in his constituency since Wednesday.
Mr Johnson, Mr Hancock and Mr Whitty are all self-isolating and continuing to work.
The Prime Minister is likely to face further criticism after Mr Jack, the Conservative MP for Dumfries and Galloway, followed ministerial his colleagues into isolation.
Mr Johnson sat next to Mr Jack as he took Scottish questions at the despatch box in the House of Commons on Wednesday, immediately before Prime Minister’s Questions.
Mr Hancock was sitting on the other side of the Scottish Secretary on the Conservatives’ front bench.
