The Queen will probably be treated with a drip and isolated during her treatment for gastroenteritis, a medical expert has said.
Professor Christopher Hawkey, at the University of Nottingham's faculty of medicine and health sciences, said:
The likely cause with the Queen is the norovirus, the winter vomiting virus.
It's very infectious and strikes in winter because people are indoors and it spreads more easily.
Because it is infectious we try to not admit people to hospital as it can start the outbreaks we hear of.
But not everyone can keep up with oral hydration so it is pretty routine to go to hospital and have a drip and wait for the thing to pass and keep yourself hydrated.