Addenbrooke's Hospital in Cambridge is asking people not to visit the hospital unless "absolutely necessary due to increased cases of flu."
The hospital says it has put plans into place to manage the outbreak, but are appealing for people to help them prevent the spread.
Anyone with symptoms of flu is advised not to visit the hospital, including the food areas until they have been free from symptoms for 48 hours.
The hospital also said:
If you are unwell and require medical advice, please contact NHS 111
Only attend the hospital if advised
Or, only attend if it is an emergency