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.
The US military has launched strikes on Iran after it struck a container ship on Sunday, while Tehran said it had closed the Strait of Hormuz again and some Gulf states announced they are under attack.
Qatar's Ministry of Interior has announced that three people have sustained injuries as a result of falling debris from interception operations against Iranian missiles and drones on Sunday.
At least two children have been killed after a ferry carrying more than 35 people collided with a bridge while crossing the Euphrates River in the eastern Syrian city of Deir al-Zor on Sunday, the Syrian Civil Defence said.
US Senator Lindsey Graham, a key Republican who went from a vocal critic of Donald Trump to one of his most loyal allies on Capitol Hill after Trump became president, has died at age 71.
The National Emergency and Crisis Management Authority (NCEMA) has stated that the situation across the UAE remains stable with "no indications of concern", and clarified that the Iranian missile threats detected early on Sunday were outside the country's borders.
UAE President His Highness Sheikh Mohamed bin Zayed Al Nahyan has extended his condolences to Qatari Emir Sheikh Tamim bin Hamad Al Thani on the passing of his father and former Emir Sheikh Hamad bin Khalifa Al Thani.
The United Arab Emirates held separate conversations with delegates from Qatar and Jordan on Saturday to discuss the latest developments in the region.