Boris Johnson is self-isolating after coming into contact with someone who tested positive for Covid-19, Downing Street has said.
The PM was contacted by NHS Test and Trace but is not showing symptoms.
BBC political correspondent Nick Eardley said the PM spent about 35 minutes with Ashfield MP Lee Anderson, who has since tested positive.
In April, Mr Johnson spent three nights in intensive care after falling ill with the virus.
He later said it “could have gone either way” and thanked healthcare workers for saving his life.
In a statement, a No 10 spokesman said: “The prime minister has today been notified by NHS Test and Trace that he is required to self-isolate as a contact of someone who has tested positive for Covid-19.
“The prime minister will follow the rules and is self-isolating.
“He will carry on working from Downing Street, including on leading the government’s response to the coronavirus pandemic.
“The PM is well and does not have any symptoms of Covid-19.”
Conservative MP Mr Anderson posted on his Facebook page to say he was self-isolating.
“On Friday I lost my sense of taste at the same time my wife had a bad headache,” he said. “I had no cough, no fever and felt well. We both had a test on Saturday and the result came in Sunday morning.
“My wife and I both tested positive. I feel absolutely fine and my biggest concern is my wife who is in the shielded group.
“But we are both feeling good.”