Two Dunedin Hospital wards are closed because patients have vomiting or diarrhoea, but test results so far have been negative for norovirus and rotavirus.
General medicine ward 8B was closed on Monday morning after six patients fell ill and seven patients had symptoms yesterday afternoon.
A ward for the elderly, 6B, was closed on Monday afternoon because six patients and one staff member were sick with the same symptoms.
Another staff member had since become sick.
Otago-Southland medical officer of Health Dr John Holmes said in a statement it was not yet known if the outbreak involved an infectious disease, one type of illness or a variety of conditions.
No new patients were being admitted to the closed wards and visiting was restricted.
Anyone wishing to visit needed to contact the hospital first.
A third ward, medical ward 8A, also had three patients and a staff member with diarrhoea and/or vomiting, but was still open.
Dr Holmes said the outbreaks were not believed to be related.
They follow outbreaks in Ward 10A at Wakari Hospital, which was closed for five days, reopening on October 27.
Eight staff and six patients had diarrhoea after the illness was brought in from the community.
The orthopaedic ward 3B at Dunedin Hospital was also closed on October 16, reopening on October 20.
One staff member and eight patients were infected.
It was not related to the Wakari outbreak.
Dr Holmes said there was also an outbreak of vomiting and diarrhoea in at least one rest-home.
He reminded people of the importance of thorough hand-washing and drying after going to the toilet and before preparing or eating food.
Those who were ill should avoid preparing food, which was not going to be cooked, for others.
People with such illnesses needed to stay away from work or school until they had been symptom-free for 48 hours, and not visit people in hospitals or rest-homes, Dr Holmes said.
