It's inevitable someone will die if the "out of control" Auckland measles isn't contained, a vaccine researcher has claimed.
There have now been more than 700 cases of the highly infectious disease, making this the biggest outbreak of the 21st century.
Another 33 were added to the tally on Wednesday.
"This is not something under control. It does appear to be out of control," University of Auckland vaccine researcher Helen Petousis-Harris told The AM Show on Thursday.
"That's when we probably aren't going to be able to trace all of the contacts of these cases, vaccinate them, isolate them and stop it from spreading. We tried to contain - we've done that in the past - but this one took on a life of its own. It doesn't appear to be something under control."
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More than half of the cases - 475 overall, with 18 new ones on Wednesday - have been recorded in the Counties Manukau DHB area, which has opened a dedicated measles ward at Middlemore Hospital to deal with the sheer number of cases.
"I was visiting the other day, and it was [chaos]," said Dr Petousis-Harris.
"They were working way over capacity with taking on these cases... It's found its patch, I guess. There's lots of people in the community - especially in the south Auckland community - still unvaccinated, especially in the older age groups, allowing it to transmit."
The last recorded measles death in New Zealand came in 1991, when seven people died in an outbreak that infected 7000 people. This is in line with the US Centers for Disease Control's estimate that around one in 1000 people who catch the disease will die from it.
"I don't think we expected to see this coming back up in the 21st century," said Dr Petousis-Harris.
"We've had deaths before in this country - fortunately not since 1991. But you keep accumulating enough cases, it's ultimately inevitable... a vaccine's going to stop that from happening."
Even if measles doesn't kill you, Dr Petousis-Harris says it leaves you more susceptible to catching other diseases.
"The measles virus can give you what we call immune amnesia - you have the measles, you recover, and then your immune system has forgotten the immunity it had for a whole lot of things you were already immune to. This amnesia can last for over two years. You can go and get a whole lot of infections, you're more likely to get sick after you get the measles. And that lasts for years."
The only upside is that it leaves you with "awesome protection" against future potential measles infections.
Manurewa High School, right in the middle of the Counties Manukau DHB area, has banned anyone from coming to class until next week unless they can demonstrate they have been vaccinated or are otherwise immune to measles.
"It's vital that you either demonstrate that you're immune or you stay away," said Dr Petousis-Harris, who would support all schools and education facilities banning enrolments of anyone who isn't vaccinated - but is confident the current outbreak can be stopped without resorting to such extreme measures.
As for anti-vaxxers - whom the World Health Organisation has labelled one of the top 10 threats to global public health - Dr Petousis-Harris says she has "absolutely nothing to say to them".
Associate Health Minister Julie Anne Genter pulled out of a planned interview with The AM Show, citing sickness. The Ministry of Health, Counties Manukau DHB and Auckland Regional Public Health Service all declined to be interviewed.