Prince William had Covid-19 in April but kept it a secret.

Prince William contracted Covid-19 in England in April but kept his diagnosis a secret, the BBC and The Sun, England’s largest paper, have reported, citing information from sources within Kensington Palace. A person close to the palace confirmed the accuracy of the reports, but did not offer additional details.

The Duke of Cambridge is likely to have contracted the virus around the same time as his father, Prince Charles, but did not reveal the information for fear of alarming the public, according to British news media. He was treated by palace doctors while isolating at his family home Anmer Hall, in Norfolk, and carried out more than a dozen business calls during this time, The Sun reported.

Prince William’s decision not to disclose his diagnosis raised questions about the palace’s secrecy since he is second in line for the throne. Buckingham Palace disclosed his father’s illness in March, which aroused alarm about the health of Queen Elizabeth II, since Charles met his mother not long before he showed symptoms.

The queen, who has isolated herself in Windsor Castle and her summer residence, Balmoral Castle in Scotland, has not been ill, according to Buckingham Palace. She addressed the nation about the response to the pandemic in April and, in July, conferred a knighthood on Tom Moore, a retired British Army captain who raised nearly $40 million for the National Health Service.

Downing Street came under fire in May after reports, weeks after the fact, that Mark Sedwill, the cabinet secretary and top civil servant in the government, had been sick with Covid-19 when the coronavirus first erupted in the spring.

The virus swept through the British halls of power in April, sickening the prime minister, Boris Johnson; the health secretary, Matt Hancock; the government’s chief medical adviser, Chris Whitty; and Mr. Johnson’s most influential policy adviser, Dominic Cummings.

Mr. Cummings came under fire for violating lockdown rules by driving 260 miles to his parents’ home in Durham, in the north of England, to recuperate. He rejected calls to resign when the news of his trip emerged several weeks later.

Cases in England recently surpassed one million, and the country is set to enter a second nationwide lockdown, with pubs, restaurants, gyms and nonessential shops closing for four weeks beginning on Thursday.

“Now is the time to take action because there is no alternative,” Mr. Johnson said at a news conference on Sunday. “We must act now to contain this autumn surge,” he said.