An Auckland resident who now has a confirmed case of measles flew Auckland to Napier return this week, before they realised they had the viral illness.
The person, whose gender or age cannot be identified due to privacy, flew to and from Napier on Air NZ flights on Tuesday.
Auckland Regional Public Health Service (ARPHS) is asking passengers on the flights, Air NZ 5025 from Auckland to Napier departing at 6.40am and Air NZ 5020 from Napier to Auckland departing at 4.40pm, to check their immunity to measles.
ARPHS public health medicine specialist Dr Maria Poynter said fellow passengers, plus anyone in the Auckland or Napier domestic terminals around the time of the flights, should also watch for signs of measles.
A Hawke's Bay District Health Board spokeswoman said only people who were on those flights and not immunised needed to watch out for symptoms.