Queen Elizabeth, 95, has tested positive for COVID and is experiencing mild symptoms, Buckingham Palace said on Sunday.
"The queen has today tested positive for COVID," the Palace said. "Her Majesty is experiencing mild cold like symptoms but expects to continue light duties at Windsor over the coming week.
"She will continue to receive medical attention and will follow all appropriate guidelines."
Charles, 73, the heir to the throne, earlier this month pulled out of an event after contracting coronavirus for a second time. A palace source said he had met the queen just days before.
The health of the queen, the world's oldest and longest-reigning monarch, has been in the spotlight since she spent a night in hospital last October for an unspecified ailment and then was advised by her doctors to rest.
Elizabeth on Wednesday quipped to members of the royal household that she could not move much as she carried out her first in-person engagement since Charles tested positive.
Israel struck the outskirts of Beirut on Sunday for the first time since the US announced a truce plan for Lebanon last week, and an Iranian lawmaker threatened to retaliate, putting talks to end the wider war into new jeopardy.
The US naval blockade of Iran and its green light on Sunday for Israel to escalate attacks in Lebanon make US bases and Israeli assets in the Middle East legitimate targets, Iran's top negotiator said in a post on X.
Ukraine President Volodymyr Zelenskyy arrived in the United Kingdom on Sunday for a series of high-level meetings focused on the war in Ukraine, European security and diplomatic efforts to end the conflict.
Israeli strikes on a Hamas-run police station and a vehicle in the Gaza Strip killed at least nine people and wounded 20 others, health officials said, as mediators began new efforts to salvage a fragile US-brokered ceasefire deal.
Kuwaiti air defences were intercepting missile and drone attacks of undisclosed origin, state media reported, while in Bahrain sirens sounded and residents were urged to seek shelter after US and Iran exchanged fire.