BRUSSELS (AP) — European Union chief Ursula von der Leyen was forced to leave an EU summit Thursday shortly after it opened because one of her close staffers tested positive for COVID-19.

She said that she herself tested negative but “as a precaution I am immediately leaving the European Council to go into self-isolation.”

Von der Leyen had already been mingling with other EU leaders ahead of the formal opening of the two-day summit. Organizers had taken special precaution to keep leaders apart and make sure they respect all health regulations.