Hundreds of people may have been exposed to measles by an infected child on board a flight from Kuala Lumpur to Auckland.
Malaysian Airlines flight MH131 arrived in Auckland last Thursday 26 February but it was only today that lab results confirmed measles.
Medical Officer of Health Dr Julia Peters said public health officials were trying to track down about 80 people who were in the 11 rows directly behind the infected child and were most at risk.
"But because measles is very infectious, and because people tend to move around on planes, we want to advise anyone on the flight that if they did start to develop symptoms that were of concern, that they needed to call their GP or their practice nurse or Healthline for advice."
Dr Peters said it could take up to 14 days for someone who had caught measles to start showing symptoms.
She said it was vital that people who felt unwell and suspected they could have measles stayed home and phoned their GP or Healthline, rather than risk infecting other people with the highly-contagious airborne disease.
She said officials were still working to identify other people the child may have been in contact with in the last ten days.