Three cases of measles have been confirmed in the South Island.
Canterbury district health board's medical officer of health Dr Ramon Pink said the cases were reported in Christchurch, Wanaka and Queenstown.
All three people were likely to have been exposed in Queenstown Airport on either 21 March or 22 March, he said.
The Southern and Canterbury DHBs have identified anyone in close contact with the three people, none of whom were immunised.
Dr Pink said anyone else who had been exposed who wasn't immunised was likely to fall ill this month.
People should call their doctor for advice if they thought they had been exposed and avoid visiting clinics in the first instance, he said.