More than 100 new cases of the measles have been confirmed in the past week, according to new figures from the Institute of Environmental Science and Research.
That brings the total number of confirmed cases to 651, a figure that health professionals have warned may steadily rise.
There are now four ongoing outbreaks, with Counties Manukau and Waitematā the two worst affected district health board areas.
Dr Jill Sherwood from the ESR says the figures were worrying and it was important people ensured they were up-to-date with their vaccinations.
It had been hoped that early efforts by public health services to quarantine patients and encourage immunisation would keep the numbers down, but Dr Sherwood says low vaccination rates meant the disease continued to spread.
"Once you have a lot of people who have been infected, there is a lot of people to try and chase up to try and control the further spread," she says.
"It's certainly looking, in the Auckland region, as if that is becoming very difficult to do with the level of vaccination in the community."
People who had developed measles-like symptoms needed to phone their GPs first, rather than visit a clinic and risk spreading the disease further, says Dr Sherwood.
But most importantly, she said, was that people needed to get vaccinated.
"If you're not certain that you've had two doses of a measles-containing vaccine from the age of 12 months onwards, then you are eligible for free vaccinations and we really encourage people to do that."
Measles is a highly-infectious viral illness spread by contact with respiratory secretions through coughing and sneezing.
People are infectious from five days before the onset of the rash to five days after the rash starts.
Infected persons should stay in isolation - staying home from school or work - during this time.
The best protection from measles is to have two MMR vaccinations. MMR is available from your family practice and is free to eligible persons.
People are considered immune if they have received two doses of MMR vaccine, have had a measles illness previously, or were born before 1969.
Anyone believing they have been exposed to measles or exhibiting symptoms, should not go to the ED or after hours' clinic or general practitioner. Instead, call the GP first.