Some visitors to North Shore Hospital have been passing Covid-19 on to patients, according to the Ministry of Health.
In a statement the ministry said it would like to remind people who are unwell not to visit others in hospital.
"There is evidence of visitors to North Shore Hospital passing Covid-19 on to patients," the ministry said.
It said there had been an increase in the number of Covid-positive Waitematā inpatients, including an outbreak at a community site.
It urged visitors to be respectful of hospital rules, wear a mask at all times, practice good hand hygiene and cough/sneeze etiquette and maintain physical distancing of at least 1 metre.
On Monday there were 6498 new cases of Covid-19 and 487 people in hospital with the virus.
There were also eight deaths reported from the past two days.