Auckland's Middlemore Hospital is on alert after an outbreak of the stomach bug norovirus.
More than one ward has been affected by the virus, the hospital said, with staff and patients also becoming sick.
Viral gastroenteritis, or norovirus, is a stomach bug which causes nausea, cramps, diarrhoea and vomiting.
Several people have been admitted to Middlemore with the illness in the last few days, it said, with some patients transferring the bug to other patients and staff.
"As of today, there are 11 patients and three staff affected," the hospital said in a statement.
It has called on people to avoid visiting the hospital if they are showing signs of the illness, and to make sure they are thoroughly washing their hands.
"We are asking that anybody who is visiting patients at Middlemore Hospital be well and show no symptoms of illness and have been symptom-free for at least two days," it said today.
"Visitors to affected wards of the hospital may be asked to wear gloves and gowns before entering. We do not recommend bringing children in to the hospital during a norovirus alert.
"We are also asking that visitors perform rigorous hand washing with soap and water before and after visiting Middlemore. Hand gel is not effective for gastroenteritis but continues to provide protection for other hand hygiene measures."
The public is also being advised to wash their hands with soap and water after using the toilet and before preparing food.
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