The Christchurch child diagnosed with measles has passed the infectious period and has been given the green light to return to preschool, with no secondary cases being reported to health authorities.

Canterbury DHB Community and Public Health was last week notified of a case of measles in a 4-year-old Christchurch child.

The child had not completed their measles, mumps and rubella (MMR) vaccinations after having received their first dose - which is given at 15 months - and was not yet old enough for their second given at 4 years of age.

Canterbury Medical Officer of Health Dr Daniel Williams said the child was diagnosed relatively late in their mild illness.

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The child's parents had done everything right to date, as far as vaccinations went, he said.

The source of the infection is still being investigated by CDHB staff.

If a child is suspected of being the index case, then the CDHB will ask for them to be blood tested, Dr Williams said.

Staff were working closely with the two pre-schools the child attended to look for the source, but also to ensure the risk of spreading the infection further is minimised.

Felicity Williams of Mozarts Performing Arts kindergarten, which was one of the preschools the child attended, said "two or three" unimmunised children were asked to stay away from kindergarten during the risk period.

The affected child is past the infectious period now and all children are safe to return to the kindergarten, Dr Williams said.

He said advice had been given to parents at preschools the child attends.

"The advice urges parents who have not immunised their children to do so. People who choose not to vaccinate their children against infectious diseases are putting not only their own children at risk, but also other people's children," he said.

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Ms Williams praised the CDHB for its swift actions.

The kindergarten was immediately given an information letter to circulate around its parents.

"We are responsible in situations like this for being able to supply information efficiently to the health department, and I'm glad to say that our student management system stood up to that and we were able to very quickly supply information to the people here," said Ms Williams.

"We've been able to move very quickly to reassure parents, who naturally get concerned, and this has been effective."

New measles outbreaks are the result of New Zealand's historically low vaccination rates, says immunisation expert Dr Nikki Turner.

Dr Turner, director of the Immunisation Advisory Centre, told Newstalk ZB this morning that New Zealand currently had very good vaccination rates among young children.

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"This is New Zealand history we're suffering from," she said.

"For a long time we had really low immunisation coverage so a large among of people walking around in the New Zealand community are not vaccinated for measles."

Last week it was also revealed a passenger on board a flight from Kuala Lumpur to Auckland had measles and was infectious.

Passengers on Malaysian Airlines Flight 131 on February 26 were urged to be vigilant for symptoms, and call their doctor before visiting if they felt unwell.

The initial symptoms of measles include a fever, running nose, cough and sore eyes.

Dr Turner said the anti-vaccine movement was not widespread enough in New Zealand to have a major impact.

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"The anti-vaccine movement is probably about 2 to 3 per cent and the rest of us make up for that by vaccinating our kids," Dr Turner said.

"The problem is historically we were not good at vaccinating for a whole lot of reasons."

Dr Williams said measles was a serious illness.

In New Zealand, around a quarter of people who catch measles end up in hospital -- and even with the best treatment, one in 1000 people will die.

"The good news is that measles vaccination is extremely effective. Once you've had a full course of vaccination against measles, you are unlikely to get it," he said.

"But because measles is so infectious, we need to maintain high levels of vaccine in the community to make sure the disease can't spread."

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Two more suspected cases have been notified to the Canterbury DHB in the past week but both cases have returned negative results.

There have been no other confirmed cases, and there has not been any secondary cases, Dr Williams said.