Boris Johnson is self-isolating for seven days having tested positive for coronavirus.
The prime minister, 55, tweeted a video message confirming he has COVID-19, writing: "Over the last 24 hours I have developed mild symptoms and tested positive for coronavirus.
"I am now self-isolating, but I will continue to lead the government's response via video-conference as we fight this virus."
Health Secretary Matt Hancock has also caught the virus and is self-isolating at home.
Downing Street said Mr Johnson was tested on the advice of his chief medical officer Professor Chris Whitty on Thursday afternoon, having been experiencing "mild symptoms" earlier the same day.
The test was carried out in Number 10 by NHS staff and the positive result was confirmed at around midnight, they added.
"He is continuing to lead the government's response to coronavirus," a spokesperson confirmed.
