Two wards have been closed at Dunedin Hospital and infection and prevention-control measures are in place following a gastroenteritis outbreak.
Southern District Health Board chief operating officer Hamish Brown said the virus was detected at the hospital last Monday, but it was difficult to identify when or how it came into the premises.
"What we can say is that infection and prevention control measures were implemented immediately to limit the spread, working alongside our public health team."
He said norovirus had been confirmed in two wards, and staff were awaiting test results on a third.
"At present, we have confirmed 15 patients and six staff have had or currently have the virus.
"The affected wards are presently closed to visitors and we are not allowing any patients in or out of these wards."
Mr Brown advised affected people to stay away from work, school, or preschool until they had been symptom free for at least 48 hours.
"Symptoms include nausea, vomiting, abdominal cramps and diarrhoea. Vomiting is more common in young people, and diarrhoea in adults.
"Generally, symptoms begin one to two days after exposure to the virus, and symptoms last one to two days."
