Another ward is closed at Scunthorpe hospital due to an outbreak of diarrhoea and vomiting.
But a medical expert has reassured people that the illness rarely causes complications.
Wards 16 and 17 at Scunthorpe hospital are closed to admissions. Anyone who has experienced diarrhoea or vomiting is urged not to visit hospital until they have been symptom free for 48 hours.
Dr Peter Cowling, Trust consultant microbiologist, said: “Patients from these wards will not be discharged to nursing or residential homes while they remain an infection risk and we have closed these wards to new admissions.
“The infection prevention and control team is reviewing the situation daily and regular and frequent disinfection is being carried out on the wards to contain the outbreak.
“We have a robust infection control policy in place. This illness lasts about 24 hours and, although unpleasant, very rarely causes serious medical problems.”
Tests will establish soon if the outbreak is due to norovirus, the winter vomiting bug.
Staff are being advised to stay off work if they have symptoms and to keep away for 48 hours after symptoms have stopped, as they will be infectious to others during this period.