Hospitals are imploring the public to only use the emergency department if they are seriously ill after record numbers in the last week.
The Waitematā District Health Board said 2600 people have turned up to EDs at - Waitākere Hospital and North Shore Hospital in the last week, 150 patients more than the same time last year.
Chief medical officer Dr Andrew Brant said hospitals had not expected the sharp rise of patients.
He believed the flu season, which arrived later than forecast, had an effect on numbers.
"It's really just hit us in the last week or two, it's hit [the whole] Auckland area and really Waitematā in particular in the last week for example.
"Why ... the timing is as it is for influenza, that's difficult to tell but we do know that it is now upon us."
Dr Brant said the winter sickness was affecting people from across the spectrum in age, gender and ethnicity.
He encouraged people to go to their family doctor or the pharmacy first and then the nearest accident and medical clinic.
Dr Brant believed the peak in sickness should ease soon.
"It's hard to know how long this particular peak and this busyness is going to be.
"We would hope with some assistance we would be over this hump ... within a week or two, if not earlier.
"But it's really getting through these particular days [that] is difficult for us when there is so much demand at the front door."