New Zealand health authorities were trying to track down hundreds of passengers on Wednesday who may have been exposed to measles on a Singapore Airlines flight at the weekend.
One passenger on the flight, which landed in Auckland on Sunday night, is now known to have been infected with the highly contagious virus.
"The passenger with measles would have been infectious at the time of their travel on this flight," said Auckland Medical Officer of Health Dr Richard Hoskins.
Health authorities were trying to trace 260 passengers on flight SQ281 and estimated they would have since been in close contact with at least another 100 people.
The passenger with measles was a New Zealander returning home.
Hoskins said measles was highly infectious and that 10 per cent of cases required hospital treatment.
Although the disease is now rare in New Zealand there were two big outbreaks in 2011, both started by people who were infected overseas.
Another outbreak late last year was confined to 11 people who contracted the disease after attending a hip-hop event in Australia.
Measles typically causes a rash, fever and white spots in the mouth.
More serious complications include blindness, pneumonia, brain damage and severe dehydration.