European Commission president Ursula von der Leyen says she has placed herself in isolation after being in contact with a person infected with coronavirus.
The head of the EU's executive arm took part in a meeting in Portugal last Tuesday that was attended by 'a person who yesterday tested positive'.
She said she tested negative for the virus on Thursday and that she will undergo another test later today.
Ms Von der Leyen, who attended a two-day summit of EU leaders in Brussels on Thursday and Friday last week, said she will be in quarantine until Tuesday morning.
Her isolation will keep her close to work, however. She has a small living quarters next to her office in the EU headquarters in Brussels.
Ms Von der Leyen said: 'I’ve been informed that I participated in a meeting last Tuesday attended by a person who yesterday tested positive for COVID-19.
'In accordance with regulations in force, I’m therefore self-isolating until tomorrow morning. I’ve tested negative on Thursday and am tested again today.'
Two weeks ago, EU Council president Charles Michel was forced to postpone a summit of EU leaders because he was quarantining.
The summit went ahead on Thursday and Friday last week and was attended by Ms Von der Leyen.
Ms Von der Leyen took part last Tuesday in a special meeting of Portugal's state council in the coastal town of Cascais, on the outskirts of Lisbon.
State councillor Antonio Lobo Xavier tested positive for the virus on Sunday.
The meeting was attended physically by 15 of the 19 members of the president's advisory body.
Portugal's president, prime minister and the parliamentary president and five state councillors were tested on Sunday and were negative, media reported.
It is up to individual commissioners to decide what travel and which in-person meetings are essential, according to Commission protocol.
Von der Leyen's team has said her Lisbon trip was essential and justified deviating from the Commission's rule banning most business trips.
More tests are taking place today.
Boris Johnson has set an October 15 deadline for deciding whether a post-Brexit trade deal is possible as the UK and EU agreed to 'intensify' talks.
The PM told Ms Von der Leyen that 'time is running out' to break the deadlock over fishing rights and state aid rules.
Amid fears that Brussels will try to run down the clock to secure concessions, Mr Johnson made clear in a phone call on Saturday night that Britain is ready to trade on 'Australian' terms - without any framework in place.
Unless the structure of a deal has emerged by the time of a summit of EU leaders on October 15, the UK has threatened to walk away and focus on preparing for that outcome.
Wrangling and rhetoric has escalated in recent weeks as the crunch moment in the trade discussions looms.
The 'standstill' transition period is set to end on January 1 whether or not there is an agreement.
© Associated Newspapers Ltd.