Prince William was diagnosed with COVID-19 earlier this year and kept his diagnosis a secret from the public, royal sources confirm to ABC News.
William, 38, was diagnosed with the virus in April, according to the royal sources.
The future king did not go public with the news of his diagnosis because he did not want to cause alarm, according to a report in The Sun newspaper, which first reported Prince William's diagnosis.
William's diagnosis came shortly after his father, Prince Charles, was diagnosed with COVID-19.
Charles, the 71-year-old heir to the British throne, publicly announced he had tested positive through a Clarence House spokesperson in March. Both he and Camilla, the Duchess of Cornwall, who did not have the virus, isolated at their home in Scotland, the spokesperson said at the time.
MORE: Queen Elizabeth makes rare joint appearance with Prince William in 1st public event since start of coronavirus pandemicPrince William is said to have isolated at Anmer Hall, his family's country home in Norfolk, England.
William's wife Duchess Kate and their three young children, George, Charlotte and Louis, did not contract the virus, according to royal sources.
Kensington Palace has not commented on William's diagnosis.
William questioned the pandemic early on, wondering out loud if it had been "hyped up" by the media.
"It does seem quite dramatic about the coronavirus," he said to a first responder in early March when he and Kate visited Dublin, Ireland. "Is it being a little hyped up, do you think, in the media?"
MORE: Prince William says coronavirus pandemic has been a chance to 'refocus our priorities'The Cambridges visited first responders in person in London later in March, before switching to virtual events while the family followed stay-at-home orders at their Anmer Hall home.
In April, the month William was diagnosed, the future king was seen on video calls thanking teachers and celebrating frontline workers, among other topics.
He also appeared with Kate and their kids to clap for health care workers, joining a nationwide initiative in the U.K.
Both William and Kate have now returned to in-person engagements.
William was by Queen Elizabeth's side last month when she attended her first public engagement since March.
He and the 94-year-old monarch traveled to the Defense Science and Technology Laboratory (DSTL), near Salisbury, their first joint appearance since 2017.