Four wards are currently closed at Hull Royal Infirmary, due to an outbreak of norovirius.
The vomiting and diarrhaea bug is extremely contagious and visitors are being urged to stay away, especially if they have experienced symptoms.
The wards that are closed are 8, 11, 100 and 110.
Hull and East Yorkshire Hospitals NHS Trust is urging people who have been infected to stay away from the hospital until they have been symptom free for 48 hours.
Most sickness and diarrhoea infections occur at this time of the year and throughout winter. They commonly break out in places such as schools, cruise ships and hospitals where there are lots of people in confined spaces. In previous years wards have been closed at the Trust as a result of this kind of infection.
Norovirus (formerly known as Norwalk virus) is the commonest cause of outbreaks of gastroenteritis in hospitals. The illness is usually quite mild, lasting for about 48 hours. However, people who have had symptoms can remain infectious for another 48 hours after the symptoms have gone away.
Dr Yvette Oade, executive medical director for the trust, said: "Our colleagues in Public Health have informed us that they are seeing an increase in the amount of Norovirus in the community.
"This is the time of year when we like to request that people coming to hospital as visitors use their common sense.
"If you have experienced diarrhoea or vomiting symptoms, then please do not visit the hospital until you have been symptom free for more than 48 hours.
"Norovirus is extremely infectious and can spread rapidly through our patients and staff causing significant discomfort and disruption to the day-to-day running of the hospital.
"If you do have these symptoms then the most appropriate place to seek advice is at your local pharmacy or NHS Direct on 0845 46 47. If symptoms persist, you might want to consult your GP.
"The Emergency Department is not the best place to come with sickness and diarrhoea.
"The infection is actually quite mild and the best course of action is to drink plenty of fluids and stay at home."