Auckland Regional Public Health Service has warned that about 900 people could have been exposed to measles in Auckland.
The news comes after it was announced on Tuesday that a further five people in Auckland have been diagnosed with the highly infectious disease, bringing the city's total to nine confirmed cases.
A further 59 people were in quarantine, ARPHS confirmed on Thursday morning.
Those who could have been exposed have been contacted by health authorities.
Auckland medical officer of health William Rainger told Radio NZ last night that people may have been exposed through waiting rooms or lecture theatres or different events.
On Tuesday, a woman in her 40s from Rodney was said to have visited the Countdown supermarket in Silverdale, the Orewa Countdown and Oliver's Cafe on March 18.
On Wednesday March 20, she visited the Four Square in Parakai at 4.30pm.
"We provide those people with advice about what to do if they develop symptoms, and to get immunised," Rainger said.
"We've got 59 people who are in quarantine at the moment, so that's people we're asking to stay at home during the incubation period in case they develop measles.
"It's a reasonably large number of people that we're following up at the moment and our objective is to prevent the spread of the virus further in the community."
In the RNZ interview, Rainger said health authorities expected more cases of the disease imported into Auckland but it was not yet an outbreak.
"Whether we are going to get sustained transmission from person to person within Auckland, we don't know if that's going to happen yet. That's when numbers would start to go up quickly. We're not in that state at the moment."
There have been 61 confirmed measles cases nationwide, with more than half of these in Canterbury.
The Auckland Regional Public Health Service are advising people to consult with their general practice if they think they have been exposed to measles, but suggest phoning first.
The symptoms include fever, cough, runny nose, sore red eyes and white spots inside the mouth. After three to five days a rash appears on the face and then moves down the body.
For more information or advice on measles, please call Healthline on 0800 611 116 or see the Auckland Regional Public Health Service website.