The Chesterfield Royal Hospital is urging visitors to stay away if they have experienced any symptoms of Norovirus within the last 48 hours.
Some wards have been affected by the virus, typical symptoms include diarrhoea and vomiting, that remains infectious up to two days after symptoms subside.
A spokesperson at the Royal said: "The hospital has noted a few occasions where people have visited wards and experienced symptoms which has resulted in a Norovirus outbreak and, whilst it is unpleasant, for most people it will pass in a couple of days with rest and plenty of water.
"However, for patients with underlying health conditions it can be much more serious and even fatal.
"Visitors are urged to stay away from the hospital if they have experienced symptoms within the last 48 hours, ensure they wash their hands with soap and hot water before and after visiting a patient area and observe all hand hygiene instructions carefully to prevent it spreading further."