Prince William, the Duke of Cambridge and second in line to the British throne, tested positive for coronavirus in April, British media reported Sunday.
Reached by NBC News on Sunday night, Kensington Palace did not confirm or deny the reports. The Sun, a British tabloid, first reported the diagnosis, citing an unnamed Kensington Palace source.
Unlike William's father, Prince Charles, who announced a positive COVID-19 test in March, William, 38, kept his diagnosis secret. It wasn't immediately clear how serious his condition was.
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The diagnosis came the same month that British Prime Minister Boris Johnson said that he'd been hospitalized in an intensive care unit after testing positive for the virus.
Johnson later revealed that his infection was so serious that he'd needed "liters and liters of oxygen" to stay alive. Doctors were preparing to announce his death, he said.
On Saturday, Johnson announced a new monthlong lockdown as the number of cases in the country topped 1 million.
"Unless we act, we could see deaths in this country running at several thousand a day," Johnson said.
The country enacted a three-month lockdown earlier this year, but the number of cases began to rise as restrictions were eased.
Under the new rules, nonessential businesses must close and bars and restaurants can only offer takeout. Schools, universities and construction sites will be allowed to remain open.