An inmate at Mt Eden remand prison has been isolated after contracting measles on Saturday.

Photo: RNZ / Diego Opatowski

The man and his cellmate are in isolation, and only staff who are immune from the contagious disease are working with them.

The sick prisoner did not leave the prison or have any visitors during the exposure period.

Any inmates who had contact with the sick man and have court appearances will stay in the prison and appear via video. They will be quarantined if they are not immune to the disease.

"We immediately made contact with Auckland Regional Public Health Service, and remain in regular contact with them to ensure we are taking all necessary action to ensure the safety and wellbeing of prisoners, our staff, contractors and visitors, and the community," said Corrections Deputy National Commissioner, Andy Milne.

The prison has almost 1000 inmates, and about 500 staff. Corrections are taking particular measures to monitor the 120 other prisoners who were in same two units as the man last week.

Visits at the prison from young children and pregnant women have been temporarily suspended.

Auckland Regional Public Health Service's Clinical Director Julia Peters said the service was helping the prison.

"ARPHS is advising Corrections regarding those who may have exposed to the virus, and therefore at risk of developing measles if they are not immune.

"The prison is actively taking steps to ensure that any risk is contained. Measles can spread quickly in a communal environment," Dr Peters says.

More measles cases in Auckland

Nationwide 54 people contracted measles last week - the largest number so far this year - with 50 in Auckland, mostly in the Counties Manukau area.

From last month, health authorities in Auckland started giving out the measles vaccine at one year instead of 15 months, in an effort to curb the region's outbreak of the disease.

There was one case each in Waikato, Hawke's Bay, Capital and Coast and Canterbury.

About a third of all cases are children under nine years old, and the next most common group is people in their 20s.

About 85 percent of those infected are people who have not been vaccinated.

In total 407 people have been confirmed to have had measles in New Zealand this year.

Measles is highly contagious and infects about 90 percent of people who come into contact with it who are not immune. It can live in the air for hours after a person has been coughing and sneezing in the area, and it can take a fortnight for symptoms to show.

Early symptoms include fever, cough, runny nose and watery 'pink' eyes, and sometimes small white spots on the back inner cheek. Measles can lead to complications including pneumonia and, in rarer cases, brain swelling or death.

One dose of the vaccine will prevent measles in 95 percent of people, while two doses will protect 99 percent of people.

People who think they might have measles are advised not to visit their doctor but instead call their GP to avoid spreading the illness.

The disease has been on the rise across the world in recent years, with cases tripling worldwide.

Measles facts: