The largest outbreak of measles in Auckland in over a decade is showing no signs of abating, with new cases being reported daily and a risk of it spreading elsewhere as families go away for the school holidays.

There have now been 72 confirmed cases of the highly-infectious illness - five of which have required hospitalisation - and over 400 people quarantined, Auckland Regional Public Health Service (APRHS) medical officer of health Richard Hoskins said.

"In the last couple of weeks we've been getting a higher proportion of cases that we can't link back to previous cases. That's indicating that it's spreading in the community and the quarantining we're doing of people isn't going to curtail the spread, so it's really down to good immunisation levels now."

To illustrate how infectious measles is, Dr Hoskins said if no one in a community was immunised, one infected person would generally spread it to between 13 and 18 others.

The current outbreak was brought to New Zealand from the United Kingdom by a west Auckland school student, who quickly infected six non-immunised people in his classroom of 30.

"At the moment there is a real risk of people getting measles, and they won't necessarily know who they get it from - it could be from just about any indoor setting. The only way to protect them against it is to get up-to-date with the MMR (measles, mumps and rubella) immunisation," Dr Hoskins said.

Although most people understood the importance of staying isolated after coming into contact with the illness, there were a few who refused stay quarantined.

At least two of these people had since developed measles and may have spread it to others in the community.

"It's really difficult to be in quarantine at home - I'm not suggesting that this is easy or that people's reasons not to be aren't legitimate - but if people know they've been in touch with somebody with measles and are not immunised then they actually need to care for their friends and community and quarantine themselves."

The time people were having to take off work and school was also having a large economic impact.

While the outbreak is currently confined to west, south and central Auckland and the North Shore, the school holidays meant families would travel and people would engage in different sorts of activities, which increased the risk of it spreading to other areas and sectors of the community.

"And If people are travelling overseas in the holidays, we could become an exporter of measles," Dr Hoskins said.

Common symptoms of measles included a runny nose, cough, sore eyes and fever, followed by a raised red rash that starts on the face and moves to cover the rest of the body.

Anyone displaying symptoms of measles should immediately telephone their doctor for advice, or Healthline on 0800 611 116.

The current outbreak is by far the largest in Auckland since 1997, Dr Hoskins said.