ESR public health physician Dr Jill Sherwood said there appeared to be three outbreaks still circulating in the community - one in Wellington, one in Auckland and one in Northland.
"It is of concern that the cases are continuing to show up," she said. "The more we've got out there in the community when we don't have high enough vaccination rates, the more chance people can come into contact with them."
Judging by current figures, the number of people confirmed to have measles was likely to be the highest since 2011 when there were 597 cases. In 2014, there were 280 confirmed reports across the whole year but, with no sign of the outbreaks dying out, this year's figure was on track to exceed that, Sherwood said.
ESR data showed 109 people had been hospitalised with the measles this year. Fifty babies under 15 months old had caught the disease and 31 of them needed hospital treatment.
Auckland Regional Public Health Service clinical director Dr Julia Peters said there had been 13 Auckland schools affected by the current outbreak, with measles cases at two central Auckland schools, six in Counties Manukau and five schools in West Auckland.
Sherwood said it was particularly important people be aware of the disease as travel increased with the start of the school holidays next week.
People travelling to poorer countries where diseases like measles were endemic tended to take the necessary precautions but many travellers did not realise this year had seen outbreaks in the UK, USA, Canada and parts of Europe, she said.
Vaccination rates in first-world countries had been dropping over the last 20 years, she said. Part of the reason was the "Wakefield effect" which saw a number of babies, who were now teens and young adults, remain unvaccinated because of incorrect data which suggested a link between the MMR vaccine and autism.
Sherwood said the other reason was that when there was little sign of the disease, some parents did not bother with vaccines.
But, measles was a serious and highly infectious disease, she said. Once contracted, people were infectious from five days before a rash appeared until five days after.
The only thing which could stop the spread was higher vaccination rates, Sherwood said.
"The pattern is clear. Outbreaks start when measles is brought into the country by someone who has travelled in from overseas. The virus then spreads to others in the community because our vaccination rates are simply not high enough to prevent disease spread.
"Babies who are too young to be vaccinated and immuno-compromised people are particularly at risk, and protection for these groups relies on high levels of immunity in the wider community."
With the numbers only continuing to grow, Auckland Regional Public Health Service medical officer of health Dr William Rainger said the objective had changed from stopping the spread of the virus to protecting those most at risk of catching it or developing complications from the disease.
At the start of an outbreak the service focused on isolating the person with the disease and any un-immunised people they may have come into contact with.
This year the organisation had already contacted more than 4500 people exposed to measles but with the numbers still rising "this level of contact tracing is neither sustainable or effective", Rainger said.
The service had also changed the immunisation schedule to allow babies to get their first vaccination at 12 months instead of 15 months in Auckland because of the increasing number of cases.
Anyone who suspected they may have the disease should avoid contact with other people and phone their GP or call Healthline on 0800 611 116 for advice.
It is important to call first because measles is highly infectious and people with measles can infect others in the waiting room.
