The palace said in a statement that the 86-year-old queen was experiencing symptoms of gastroenteritis. She is being examined at London's King Edward VII hospital, and "as a precaution, all official engagements for this week will regrettably be either postponed or cancelled," the palace said.
The symptoms of gastroenteritis - vomiting and diarrhea - are generally mild and usually pass after one or two days, but they can be more severe in older or otherwise more vulnerable people.
Officials had said on Friday that Elizabeth was dealing with a stomach bug. She had to cancel a visit Swansea, Wales, on Saturday to present leeks - a national symbol - to soldiers of the Royal Welsh Regiment in honor of Wales' national day, St. David's Day.
Elizabeth, who celebrated 60 years on the throne last year, rarely misses engagements due to ill health. About five months ago, she cancelled an engagement due to a bad back. She had been due to visit Rome on Wednesday and Thursday.
Ingrid Seward, the editor of the British magazine Majesty, said that the queen "probably agreed to be hospitalized in order to get better quickly."
"Everybody will want to be wishing her a speedy recovery," she told Sky News television.
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