George Bush Sr has been moved into intensive care after suffering "a series of setbacks that include a persistent fever," according to a family spokesman.
Doctors are "cautiously optimistic" about the 88-year-old former president's health, he added.
Video report by Debi Edward.
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Prince Philip's final public engagement as a royal before retiring will take place in early August, Buckingham Palace has announced.
Passengers have been escorted off the Oblivion rollercoaster ride at Alton Towers after it stopped at its highest point.
Charlie Gard's parents are embroiled in a fresh High Court battle over whether the terminally ill baby can spend his final days at home.