Auckland health services are battling to contain the measles disease with a fifth case now under investigation and 100 people quarantined since the start of the outbreak this month.
Dr Julia Peters from the Auckland Public Health Service told TVNZ's Breakfast today that her staff are getting more cases and they're working very hard to contain this.
However, she said it is disappointing when people quarantined disobey medical instructions.
"We want people to co-operate with us and follow our instructions... it's important for people to know that this is a really infectious disease," Dr Peters said.
Her comments were aimed at a man who defied quarantine instructions when he visited an apartment block and the SkyCity casino.
"So we've had a secondary case from the first two cases and we want to avoid getting more of those," she said.
Dr Peters says the infectious disease can spread before one has any symptoms, but the first symptoms are like a common cold, feeling miserable then followed by the rash.
She says the only way to prevent the disease is for everybody to be fully immunised.
People who are concerned about possible symptoms should contact their GP, she said.