EU boss Ursula von der Leyen is in isolation after being in contact with a person infected with the coronavirus, she said today.
The European Commission President has tested negative but is staying away from others as a precaution.
She tweeted about the news this morning, saying the meeting was last Tuesday.
She said she had already tested negative on Tuesday and would have a further test today.
Ms Von Der Leyen spoke with Boris Johnson over the phone on Saturday about the ongoing Brexit talks.
Both sides urged their negotiators to work at pace in the coming days to reach a deal.
Von der Leyen said she will be in quarantine until Tuesday morning.
She has a small living quarters next to her office in the EU headquarters in Brussels.
Two weeks ago, EU Council President Charles Michel was forced to postpone a summit of EU leaders because he was quarantining.
Boris has said he wants a Brexit deal done by the middle of October to have time to get it implemented by the end of the year – but the coronavirus has already distracted attention from both sides over the last six months.
Britain will leave the transition period on December 31 no matter what, the PM has insisted.
A deadline has been set for 14 October to get an agreement on the table.
However, last week Chief eurocrat announced legal action against the UK over the PM’s controversial Brexit legislation – which could result in fines running into hundreds of millions of pounds.
Downing Street missed a midnight deadline to withdraw controversial clauses from the Internal Market Bill and pressed ahead anyway.
Government insiders said the legal threats were a common tool the EU regularly use against member states – and that last year alone there were 800 open cases.