Middlemore Hospital in South Auckland is taking extra precautions to protect against norovirus after more than a dozen people there fell ill with the stomach virus.
Eleven patients and three staff from at least two wards have caught the gastro-intestinal infection.
"There have been several admissions over the last few days of patients with gastro-enteritis from the community, and secondary transmission has occurred to staff and patients in more than one ward," said spokeswoman Lauren Young.
The hospital's last outbreak of the infection was in 2012, when more than 100 people suffered.
"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," said Ms Young. Visitors were asked to perform "rigorous hand-washing with soap and water".
What is norovirus?
* A highly contagious virus that infects the stomach and intestines.
* Can cause nausea, vomiting, abdominal pain and diarrhoea for up to 72 hours.
* Virus is spread on contaminated surfaces, in the air around an infected person who vomits, in contaminated food, through inadequately treated drinking water and by sewage pollution of shellfish beds.