Passengers on flights between Auckland and Palmerston North in early July are being warned they may have been exposed to measles.
A passenger on two Air New Zealand flights on 6 July and 7 July was travelling while infectious, Auckland Regional Public Health Service said.
The person had flown before they knew they had the disease.
The flights were NZ5119 from Auckland to Palmerston North which departed at 7.20m on Saturday 6 July and NZ5114 which left at 2.30pm on Sunday 7 July.
Public Health Service clinical director Dr Julia Peters said fellow passengers, and anyone in Auckland or Palmerston North's domestic terminals around the time of the flights, should watch for signs of measles.