Wards G3 and G5 at West Suffolk Hospital are currently closed to new admissions after several patients showed symptoms of norovirus.
Around 21 patients have shown symptoms of the highly contagious diarrhoea and vomiting virus during the past week.
The wards were closed to new admissions on Saturday.
Anyone visiting has been urged to take extra care to wash their hands with soap and water both on arrival and when leaving the hospital, while anyone who has shown symptoms of the virus has been asked to stay away.
Nichole Day, executive chief nurse at West Suffolk Hospital, said: “Norovirus is very infectious and every year there are cases in the community which transfer to the hospital. Because the virus has an incubation period of several days, people are often unaware that they are carrying it until after they have passed it on.
“We would advise anyone who has had diarrhoea or vomiting to stay away from the hospital for at least 72 hours after they have recovered, even if they feel better. Otherwise they run the risk of unknowingly passing the highly contagious illness on to someone who is already sick.
“Anyone who visits the hospital should be vigilant and take care to clean their hands. If they are visiting the affected ward, they should use soap and water when they arrive and before they leave as the alcohol gel is not effective against this virus.”