The Prime Minister's Press Secretary is in coronavirus self-isolation.
Allegra Stratton, who has served at the Downing Street Press Secretary since November, is quarantining.
It is not currently clear whether Stratton has tested positive or came into contact with someone who has.
It emerged this week that Matt Hancock is also isolating.
The Health Secretary was 'pinged' by the NHS app, meaning he'd been in contact with someone who tested positive.
Stratton, a former Newsnight journalist, was employed by Number 10 to front White House like briefings.
Her debut has been pushed back multiple times however due to the pandemic.
The briefings were due to begin in October with a former courtroom in Downing Street refurbished to provide a hi-tech studio setting where the events could take place.
That start date was pushed back to January 11, but was then put on hold once again.
“We are looking closely at the best communication for the period we now find ourselves in,” she said of the delay.
“We have a new strain of coronavirus that’s 50% more infectious; the prime minister’s taken the steps he’s taken in the last few days, and we are considering the best way to support this and to get across public health messaging.”
In the spring Boris Johnson was forced to isolate in Downing Street after contracting the virus.
He needed to receive treatment in intensive care at London's St Thomas' Hospital.
