Visitors who have experienced diarrhoea and vomiting symptoms in the previous 72 hours are being urged to stay away from the Queen Elizabeth Hospital in King's Lynn.
It comes as the hospital is experiencing a surge in patients attending with norovirus symptoms.
Dr Ian Hosein, associate medical director for infection prevention and control, said: 'It's important to let people know that norovirus is principally a food borne infection.
'I would ask visitors to please not bring self-prepared food items into our hospital. They could be accidentally contaminated with the virus, which puts patients at risk of getting the infection.
'Looking after patients with norovirus means we sometimes have to close areas to stop the virus spreading, which naturally puts the hospital under further pressure. Any support you can give in preventing more cases by washing your hands properly, not bringing food into hospital and not visiting, will be a significant help.'
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